The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_exec.c

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    1 /*-
    2  * Copyright (c) 1993, David Greenman
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  */
   26 
   27 #include <sys/cdefs.h>
   28 __FBSDID("$FreeBSD$");
   29 
   30 #include "opt_capsicum.h"
   31 #include "opt_hwpmc_hooks.h"
   32 #include "opt_ktrace.h"
   33 #include "opt_vm.h"
   34 
   35 #include <sys/param.h>
   36 #include <sys/capsicum.h>
   37 #include <sys/systm.h>
   38 #include <sys/eventhandler.h>
   39 #include <sys/lock.h>
   40 #include <sys/mutex.h>
   41 #include <sys/sysproto.h>
   42 #include <sys/signalvar.h>
   43 #include <sys/kernel.h>
   44 #include <sys/mount.h>
   45 #include <sys/filedesc.h>
   46 #include <sys/fcntl.h>
   47 #include <sys/acct.h>
   48 #include <sys/exec.h>
   49 #include <sys/imgact.h>
   50 #include <sys/imgact_elf.h>
   51 #include <sys/wait.h>
   52 #include <sys/malloc.h>
   53 #include <sys/mman.h>
   54 #include <sys/priv.h>
   55 #include <sys/proc.h>
   56 #include <sys/pioctl.h>
   57 #include <sys/ptrace.h>
   58 #include <sys/namei.h>
   59 #include <sys/resourcevar.h>
   60 #include <sys/rwlock.h>
   61 #include <sys/sched.h>
   62 #include <sys/sdt.h>
   63 #include <sys/sf_buf.h>
   64 #include <sys/syscallsubr.h>
   65 #include <sys/sysent.h>
   66 #include <sys/shm.h>
   67 #include <sys/smp.h>
   68 #include <sys/sysctl.h>
   69 #include <sys/vnode.h>
   70 #include <sys/stat.h>
   71 #ifdef KTRACE
   72 #include <sys/ktrace.h>
   73 #endif
   74 
   75 #include <vm/vm.h>
   76 #include <vm/vm_param.h>
   77 #include <vm/pmap.h>
   78 #include <vm/vm_page.h>
   79 #include <vm/vm_map.h>
   80 #include <vm/vm_kern.h>
   81 #include <vm/vm_extern.h>
   82 #include <vm/vm_object.h>
   83 #include <vm/vm_pager.h>
   84 
   85 #ifdef  HWPMC_HOOKS
   86 #include <sys/pmckern.h>
   87 #endif
   88 
   89 #include <machine/reg.h>
   90 
   91 #include <security/audit/audit.h>
   92 #include <security/mac/mac_framework.h>
   93 
   94 #ifdef KDTRACE_HOOKS
   95 #include <sys/dtrace_bsd.h>
   96 dtrace_execexit_func_t  dtrace_fasttrap_exec;
   97 #endif
   98 
   99 SDT_PROVIDER_DECLARE(proc);
  100 SDT_PROBE_DEFINE1(proc, , , exec, "char *");
  101 SDT_PROBE_DEFINE1(proc, , , exec__failure, "int");
  102 SDT_PROBE_DEFINE1(proc, , , exec__success, "char *");
  103 
  104 MALLOC_DEFINE(M_PARGS, "proc-args", "Process arguments");
  105 
  106 int coredump_pack_fileinfo = 1;
  107 SYSCTL_INT(_kern, OID_AUTO, coredump_pack_fileinfo, CTLFLAG_RWTUN,
  108     &coredump_pack_fileinfo, 0,
  109     "Enable file path packing in 'procstat -f' coredump notes");
  110 
  111 int coredump_pack_vmmapinfo = 1;
  112 SYSCTL_INT(_kern, OID_AUTO, coredump_pack_vmmapinfo, CTLFLAG_RWTUN,
  113     &coredump_pack_vmmapinfo, 0,
  114     "Enable file path packing in 'procstat -v' coredump notes");
  115 
  116 static int sysctl_kern_ps_strings(SYSCTL_HANDLER_ARGS);
  117 static int sysctl_kern_usrstack(SYSCTL_HANDLER_ARGS);
  118 static int sysctl_kern_stackprot(SYSCTL_HANDLER_ARGS);
  119 static int do_execve(struct thread *td, struct image_args *args,
  120     struct mac *mac_p, struct vmspace *oldvmspace);
  121 
  122 /* XXX This should be vm_size_t. */
  123 SYSCTL_PROC(_kern, KERN_PS_STRINGS, ps_strings, CTLTYPE_ULONG|CTLFLAG_RD|
  124     CTLFLAG_CAPRD|CTLFLAG_MPSAFE, NULL, 0, sysctl_kern_ps_strings, "LU", "");
  125 
  126 /* XXX This should be vm_size_t. */
  127 SYSCTL_PROC(_kern, KERN_USRSTACK, usrstack, CTLTYPE_ULONG|CTLFLAG_RD|
  128     CTLFLAG_CAPRD|CTLFLAG_MPSAFE, NULL, 0, sysctl_kern_usrstack, "LU", "");
  129 
  130 SYSCTL_PROC(_kern, OID_AUTO, stackprot, CTLTYPE_INT|CTLFLAG_RD|CTLFLAG_MPSAFE,
  131     NULL, 0, sysctl_kern_stackprot, "I", "");
  132 
  133 u_long ps_arg_cache_limit = PAGE_SIZE / 16;
  134 SYSCTL_ULONG(_kern, OID_AUTO, ps_arg_cache_limit, CTLFLAG_RW, 
  135     &ps_arg_cache_limit, 0, "");
  136 
  137 static int disallow_high_osrel;
  138 SYSCTL_INT(_kern, OID_AUTO, disallow_high_osrel, CTLFLAG_RW,
  139     &disallow_high_osrel, 0,
  140     "Disallow execution of binaries built for higher version of the world");
  141 
  142 static int map_at_zero = 0;
  143 SYSCTL_INT(_security_bsd, OID_AUTO, map_at_zero, CTLFLAG_RWTUN, &map_at_zero, 0,
  144     "Permit processes to map an object at virtual address 0.");
  145 
  146 EVENTHANDLER_LIST_DECLARE(process_exec);
  147 
  148 static int
  149 sysctl_kern_ps_strings(SYSCTL_HANDLER_ARGS)
  150 {
  151         struct proc *p;
  152         int error;
  153 
  154         p = curproc;
  155 #ifdef SCTL_MASK32
  156         if (req->flags & SCTL_MASK32) {
  157                 unsigned int val;
  158                 val = (unsigned int)p->p_sysent->sv_psstrings;
  159                 error = SYSCTL_OUT(req, &val, sizeof(val));
  160         } else
  161 #endif
  162                 error = SYSCTL_OUT(req, &p->p_sysent->sv_psstrings,
  163                    sizeof(p->p_sysent->sv_psstrings));
  164         return error;
  165 }
  166 
  167 static int
  168 sysctl_kern_usrstack(SYSCTL_HANDLER_ARGS)
  169 {
  170         struct proc *p;
  171         int error;
  172 
  173         p = curproc;
  174 #ifdef SCTL_MASK32
  175         if (req->flags & SCTL_MASK32) {
  176                 unsigned int val;
  177                 val = (unsigned int)p->p_sysent->sv_usrstack;
  178                 error = SYSCTL_OUT(req, &val, sizeof(val));
  179         } else
  180 #endif
  181                 error = SYSCTL_OUT(req, &p->p_sysent->sv_usrstack,
  182                     sizeof(p->p_sysent->sv_usrstack));
  183         return error;
  184 }
  185 
  186 static int
  187 sysctl_kern_stackprot(SYSCTL_HANDLER_ARGS)
  188 {
  189         struct proc *p;
  190 
  191         p = curproc;
  192         return (SYSCTL_OUT(req, &p->p_sysent->sv_stackprot,
  193             sizeof(p->p_sysent->sv_stackprot)));
  194 }
  195 
  196 /*
  197  * Each of the items is a pointer to a `const struct execsw', hence the
  198  * double pointer here.
  199  */
  200 static const struct execsw **execsw;
  201 
  202 #ifndef _SYS_SYSPROTO_H_
  203 struct execve_args {
  204         char    *fname; 
  205         char    **argv;
  206         char    **envv; 
  207 };
  208 #endif
  209 
  210 int
  211 sys_execve(struct thread *td, struct execve_args *uap)
  212 {
  213         struct image_args args;
  214         struct vmspace *oldvmspace;
  215         int error;
  216 
  217         error = pre_execve(td, &oldvmspace);
  218         if (error != 0)
  219                 return (error);
  220         error = exec_copyin_args(&args, uap->fname, UIO_USERSPACE,
  221             uap->argv, uap->envv);
  222         if (error == 0)
  223                 error = kern_execve(td, &args, NULL, oldvmspace);
  224         post_execve(td, error, oldvmspace);
  225         return (error);
  226 }
  227 
  228 #ifndef _SYS_SYSPROTO_H_
  229 struct fexecve_args {
  230         int     fd;
  231         char    **argv;
  232         char    **envv;
  233 }
  234 #endif
  235 int
  236 sys_fexecve(struct thread *td, struct fexecve_args *uap)
  237 {
  238         struct image_args args;
  239         struct vmspace *oldvmspace;
  240         int error;
  241 
  242         error = pre_execve(td, &oldvmspace);
  243         if (error != 0)
  244                 return (error);
  245         error = exec_copyin_args(&args, NULL, UIO_SYSSPACE,
  246             uap->argv, uap->envv);
  247         if (error == 0) {
  248                 args.fd = uap->fd;
  249                 error = kern_execve(td, &args, NULL, oldvmspace);
  250         }
  251         post_execve(td, error, oldvmspace);
  252         return (error);
  253 }
  254 
  255 #ifndef _SYS_SYSPROTO_H_
  256 struct __mac_execve_args {
  257         char    *fname;
  258         char    **argv;
  259         char    **envv;
  260         struct mac      *mac_p;
  261 };
  262 #endif
  263 
  264 int
  265 sys___mac_execve(struct thread *td, struct __mac_execve_args *uap)
  266 {
  267 #ifdef MAC
  268         struct image_args args;
  269         struct vmspace *oldvmspace;
  270         int error;
  271 
  272         error = pre_execve(td, &oldvmspace);
  273         if (error != 0)
  274                 return (error);
  275         error = exec_copyin_args(&args, uap->fname, UIO_USERSPACE,
  276             uap->argv, uap->envv);
  277         if (error == 0)
  278                 error = kern_execve(td, &args, uap->mac_p, oldvmspace);
  279         post_execve(td, error, oldvmspace);
  280         return (error);
  281 #else
  282         return (ENOSYS);
  283 #endif
  284 }
  285 
  286 int
  287 pre_execve(struct thread *td, struct vmspace **oldvmspace)
  288 {
  289         struct proc *p;
  290         int error;
  291 
  292         KASSERT(td == curthread, ("non-current thread %p", td));
  293         error = 0;
  294         p = td->td_proc;
  295         if ((p->p_flag & P_HADTHREADS) != 0) {
  296                 PROC_LOCK(p);
  297                 if (thread_single(p, SINGLE_BOUNDARY) != 0)
  298                         error = ERESTART;
  299                 PROC_UNLOCK(p);
  300         }
  301         KASSERT(error != 0 || (td->td_pflags & TDP_EXECVMSPC) == 0,
  302             ("nested execve"));
  303         *oldvmspace = p->p_vmspace;
  304         return (error);
  305 }
  306 
  307 void
  308 post_execve(struct thread *td, int error, struct vmspace *oldvmspace)
  309 {
  310         struct proc *p;
  311 
  312         KASSERT(td == curthread, ("non-current thread %p", td));
  313         p = td->td_proc;
  314         if ((p->p_flag & P_HADTHREADS) != 0) {
  315                 PROC_LOCK(p);
  316                 /*
  317                  * If success, we upgrade to SINGLE_EXIT state to
  318                  * force other threads to suicide.
  319                  */
  320                 if (error == 0)
  321                         thread_single(p, SINGLE_EXIT);
  322                 else
  323                         thread_single_end(p, SINGLE_BOUNDARY);
  324                 PROC_UNLOCK(p);
  325         }
  326         exec_cleanup(td, oldvmspace);
  327 }
  328 
  329 /*
  330  * kern_execve() has the astonishing property of not always returning to
  331  * the caller.  If sufficiently bad things happen during the call to
  332  * do_execve(), it can end up calling exit1(); as a result, callers must
  333  * avoid doing anything which they might need to undo (e.g., allocating
  334  * memory).
  335  */
  336 int
  337 kern_execve(struct thread *td, struct image_args *args, struct mac *mac_p,
  338     struct vmspace *oldvmspace)
  339 {
  340 
  341         AUDIT_ARG_ARGV(args->begin_argv, args->argc,
  342             args->begin_envv - args->begin_argv);
  343         AUDIT_ARG_ENVV(args->begin_envv, args->envc,
  344             args->endp - args->begin_envv);
  345         return (do_execve(td, args, mac_p, oldvmspace));
  346 }
  347 
  348 /*
  349  * In-kernel implementation of execve().  All arguments are assumed to be
  350  * userspace pointers from the passed thread.
  351  */
  352 static int
  353 do_execve(struct thread *td, struct image_args *args, struct mac *mac_p,
  354     struct vmspace *oldvmspace)
  355 {
  356         struct proc *p = td->td_proc;
  357         struct nameidata nd;
  358         struct ucred *oldcred;
  359         struct uidinfo *euip = NULL;
  360         register_t *stack_base;
  361         struct image_params image_params, *imgp;
  362         struct vattr attr;
  363         int (*img_first)(struct image_params *);
  364         struct pargs *oldargs = NULL, *newargs = NULL;
  365         struct sigacts *oldsigacts = NULL, *newsigacts = NULL;
  366 #ifdef KTRACE
  367         struct vnode *tracevp = NULL;
  368         struct ucred *tracecred = NULL;
  369 #endif
  370         struct vnode *oldtextvp = NULL, *newtextvp;
  371         cap_rights_t rights;
  372         int credential_changing;
  373         int textset;
  374 #ifdef MAC
  375         struct label *interpvplabel = NULL;
  376         int will_transition;
  377 #endif
  378 #ifdef HWPMC_HOOKS
  379         struct pmckern_procexec pe;
  380 #endif
  381         int error, i, orig_osrel;
  382         static const char fexecv_proc_title[] = "(fexecv)";
  383 
  384         imgp = &image_params;
  385 
  386         /*
  387          * Lock the process and set the P_INEXEC flag to indicate that
  388          * it should be left alone until we're done here.  This is
  389          * necessary to avoid race conditions - e.g. in ptrace() -
  390          * that might allow a local user to illicitly obtain elevated
  391          * privileges.
  392          */
  393         PROC_LOCK(p);
  394         KASSERT((p->p_flag & P_INEXEC) == 0,
  395             ("%s(): process already has P_INEXEC flag", __func__));
  396         p->p_flag |= P_INEXEC;
  397         PROC_UNLOCK(p);
  398 
  399         /*
  400          * Initialize part of the common data
  401          */
  402         bzero(imgp, sizeof(*imgp));
  403         imgp->proc = p;
  404         imgp->attr = &attr;
  405         imgp->args = args;
  406         oldcred = p->p_ucred;
  407         orig_osrel = p->p_osrel;
  408 
  409 #ifdef MAC
  410         error = mac_execve_enter(imgp, mac_p);
  411         if (error)
  412                 goto exec_fail;
  413 #endif
  414 
  415         /*
  416          * Translate the file name. namei() returns a vnode pointer
  417          *      in ni_vp among other things.
  418          *
  419          * XXXAUDIT: It would be desirable to also audit the name of the
  420          * interpreter if this is an interpreted binary.
  421          */
  422         if (args->fname != NULL) {
  423                 NDINIT(&nd, LOOKUP, ISOPEN | LOCKLEAF | FOLLOW | SAVENAME
  424                     | AUDITVNODE1, UIO_SYSSPACE, args->fname, td);
  425         }
  426 
  427         SDT_PROBE1(proc, , , exec, args->fname);
  428 
  429 interpret:
  430         if (args->fname != NULL) {
  431 #ifdef CAPABILITY_MODE
  432                 /*
  433                  * While capability mode can't reach this point via direct
  434                  * path arguments to execve(), we also don't allow
  435                  * interpreters to be used in capability mode (for now).
  436                  * Catch indirect lookups and return a permissions error.
  437                  */
  438                 if (IN_CAPABILITY_MODE(td)) {
  439                         error = ECAPMODE;
  440                         goto exec_fail;
  441                 }
  442 #endif
  443                 error = namei(&nd);
  444                 if (error)
  445                         goto exec_fail;
  446 
  447                 newtextvp = nd.ni_vp;
  448                 imgp->vp = newtextvp;
  449         } else {
  450                 AUDIT_ARG_FD(args->fd);
  451                 /*
  452                  * Descriptors opened only with O_EXEC or O_RDONLY are allowed.
  453                  */
  454                 error = fgetvp_exec(td, args->fd,
  455                     cap_rights_init(&rights, CAP_FEXECVE), &newtextvp);
  456                 if (error)
  457                         goto exec_fail;
  458                 vn_lock(newtextvp, LK_EXCLUSIVE | LK_RETRY);
  459                 AUDIT_ARG_VNODE1(newtextvp);
  460                 imgp->vp = newtextvp;
  461         }
  462 
  463         /*
  464          * Check file permissions (also 'opens' file)
  465          */
  466         error = exec_check_permissions(imgp);
  467         if (error)
  468                 goto exec_fail_dealloc;
  469 
  470         imgp->object = imgp->vp->v_object;
  471         if (imgp->object != NULL)
  472                 vm_object_reference(imgp->object);
  473 
  474         /*
  475          * Set VV_TEXT now so no one can write to the executable while we're
  476          * activating it.
  477          *
  478          * Remember if this was set before and unset it in case this is not
  479          * actually an executable image.
  480          */
  481         textset = VOP_IS_TEXT(imgp->vp);
  482         VOP_SET_TEXT(imgp->vp);
  483 
  484         error = exec_map_first_page(imgp);
  485         if (error)
  486                 goto exec_fail_dealloc;
  487 
  488         imgp->proc->p_osrel = 0;
  489 
  490         /*
  491          * Implement image setuid/setgid.
  492          *
  493          * Determine new credentials before attempting image activators
  494          * so that it can be used by process_exec handlers to determine
  495          * credential/setid changes.
  496          *
  497          * Don't honor setuid/setgid if the filesystem prohibits it or if
  498          * the process is being traced.
  499          *
  500          * We disable setuid/setgid/etc in capability mode on the basis
  501          * that most setugid applications are not written with that
  502          * environment in mind, and will therefore almost certainly operate
  503          * incorrectly. In principle there's no reason that setugid
  504          * applications might not be useful in capability mode, so we may want
  505          * to reconsider this conservative design choice in the future.
  506          *
  507          * XXXMAC: For the time being, use NOSUID to also prohibit
  508          * transitions on the file system.
  509          */
  510         credential_changing = 0;
  511         credential_changing |= (attr.va_mode & S_ISUID) &&
  512             oldcred->cr_uid != attr.va_uid;
  513         credential_changing |= (attr.va_mode & S_ISGID) &&
  514             oldcred->cr_gid != attr.va_gid;
  515 #ifdef MAC
  516         will_transition = mac_vnode_execve_will_transition(oldcred, imgp->vp,
  517             interpvplabel, imgp);
  518         credential_changing |= will_transition;
  519 #endif
  520 
  521         /* Don't inherit PROC_PDEATHSIG_CTL value if setuid/setgid. */
  522         if (credential_changing)
  523                 imgp->proc->p_pdeathsig = 0;
  524 
  525         if (credential_changing &&
  526 #ifdef CAPABILITY_MODE
  527             ((oldcred->cr_flags & CRED_FLAG_CAPMODE) == 0) &&
  528 #endif
  529             (imgp->vp->v_mount->mnt_flag & MNT_NOSUID) == 0 &&
  530             (p->p_flag & P_TRACED) == 0) {
  531                 imgp->credential_setid = true;
  532                 VOP_UNLOCK(imgp->vp, 0);
  533                 imgp->newcred = crdup(oldcred);
  534                 if (attr.va_mode & S_ISUID) {
  535                         euip = uifind(attr.va_uid);
  536                         change_euid(imgp->newcred, euip);
  537                 }
  538                 vn_lock(imgp->vp, LK_EXCLUSIVE | LK_RETRY);
  539                 if (attr.va_mode & S_ISGID)
  540                         change_egid(imgp->newcred, attr.va_gid);
  541                 /*
  542                  * Implement correct POSIX saved-id behavior.
  543                  *
  544                  * XXXMAC: Note that the current logic will save the
  545                  * uid and gid if a MAC domain transition occurs, even
  546                  * though maybe it shouldn't.
  547                  */
  548                 change_svuid(imgp->newcred, imgp->newcred->cr_uid);
  549                 change_svgid(imgp->newcred, imgp->newcred->cr_gid);
  550         } else {
  551                 /*
  552                  * Implement correct POSIX saved-id behavior.
  553                  *
  554                  * XXX: It's not clear that the existing behavior is
  555                  * POSIX-compliant.  A number of sources indicate that the
  556                  * saved uid/gid should only be updated if the new ruid is
  557                  * not equal to the old ruid, or the new euid is not equal
  558                  * to the old euid and the new euid is not equal to the old
  559                  * ruid.  The FreeBSD code always updates the saved uid/gid.
  560                  * Also, this code uses the new (replaced) euid and egid as
  561                  * the source, which may or may not be the right ones to use.
  562                  */
  563                 if (oldcred->cr_svuid != oldcred->cr_uid ||
  564                     oldcred->cr_svgid != oldcred->cr_gid) {
  565                         VOP_UNLOCK(imgp->vp, 0);
  566                         imgp->newcred = crdup(oldcred);
  567                         vn_lock(imgp->vp, LK_EXCLUSIVE | LK_RETRY);
  568                         change_svuid(imgp->newcred, imgp->newcred->cr_uid);
  569                         change_svgid(imgp->newcred, imgp->newcred->cr_gid);
  570                 }
  571         }
  572         /* The new credentials are installed into the process later. */
  573 
  574         /*
  575          * Do the best to calculate the full path to the image file.
  576          */
  577         if (args->fname != NULL && args->fname[0] == '/')
  578                 imgp->execpath = args->fname;
  579         else {
  580                 VOP_UNLOCK(imgp->vp, 0);
  581                 if (vn_fullpath(td, imgp->vp, &imgp->execpath,
  582                     &imgp->freepath) != 0)
  583                         imgp->execpath = args->fname;
  584                 vn_lock(imgp->vp, LK_EXCLUSIVE | LK_RETRY);
  585         }
  586 
  587         /*
  588          *      If the current process has a special image activator it
  589          *      wants to try first, call it.   For example, emulating shell
  590          *      scripts differently.
  591          */
  592         error = -1;
  593         if ((img_first = imgp->proc->p_sysent->sv_imgact_try) != NULL)
  594                 error = img_first(imgp);
  595 
  596         /*
  597          *      Loop through the list of image activators, calling each one.
  598          *      An activator returns -1 if there is no match, 0 on success,
  599          *      and an error otherwise.
  600          */
  601         for (i = 0; error == -1 && execsw[i]; ++i) {
  602                 if (execsw[i]->ex_imgact == NULL ||
  603                     execsw[i]->ex_imgact == img_first) {
  604                         continue;
  605                 }
  606                 error = (*execsw[i]->ex_imgact)(imgp);
  607         }
  608 
  609         if (error) {
  610                 if (error == -1) {
  611                         if (textset == 0)
  612                                 VOP_UNSET_TEXT(imgp->vp);
  613                         error = ENOEXEC;
  614                 }
  615                 goto exec_fail_dealloc;
  616         }
  617 
  618         /*
  619          * Special interpreter operation, cleanup and loop up to try to
  620          * activate the interpreter.
  621          */
  622         if (imgp->interpreted) {
  623                 exec_unmap_first_page(imgp);
  624                 /*
  625                  * VV_TEXT needs to be unset for scripts.  There is a short
  626                  * period before we determine that something is a script where
  627                  * VV_TEXT will be set. The vnode lock is held over this
  628                  * entire period so nothing should illegitimately be blocked.
  629                  */
  630                 VOP_UNSET_TEXT(imgp->vp);
  631                 /* free name buffer and old vnode */
  632                 if (args->fname != NULL)
  633                         NDFREE(&nd, NDF_ONLY_PNBUF);
  634 #ifdef MAC
  635                 mac_execve_interpreter_enter(newtextvp, &interpvplabel);
  636 #endif
  637                 if (imgp->opened) {
  638                         VOP_CLOSE(newtextvp, FREAD, td->td_ucred, td);
  639                         imgp->opened = 0;
  640                 }
  641                 vput(newtextvp);
  642                 vm_object_deallocate(imgp->object);
  643                 imgp->object = NULL;
  644                 imgp->credential_setid = false;
  645                 if (imgp->newcred != NULL) {
  646                         crfree(imgp->newcred);
  647                         imgp->newcred = NULL;
  648                 }
  649                 imgp->execpath = NULL;
  650                 free(imgp->freepath, M_TEMP);
  651                 imgp->freepath = NULL;
  652                 /* set new name to that of the interpreter */
  653                 NDINIT(&nd, LOOKUP, ISOPEN | LOCKLEAF | FOLLOW | SAVENAME,
  654                     UIO_SYSSPACE, imgp->interpreter_name, td);
  655                 args->fname = imgp->interpreter_name;
  656                 goto interpret;
  657         }
  658 
  659         /*
  660          * NB: We unlock the vnode here because it is believed that none
  661          * of the sv_copyout_strings/sv_fixup operations require the vnode.
  662          */
  663         VOP_UNLOCK(imgp->vp, 0);
  664 
  665         if (disallow_high_osrel &&
  666             P_OSREL_MAJOR(p->p_osrel) > P_OSREL_MAJOR(__FreeBSD_version)) {
  667                 error = ENOEXEC;
  668                 uprintf("Osrel %d for image %s too high\n", p->p_osrel,
  669                     imgp->execpath != NULL ? imgp->execpath : "<unresolved>");
  670                 vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
  671                 goto exec_fail_dealloc;
  672         }
  673 
  674         /* ABI enforces the use of Capsicum. Switch into capabilities mode. */
  675         if (SV_PROC_FLAG(p, SV_CAPSICUM))
  676                 sys_cap_enter(td, NULL);
  677 
  678         /*
  679          * Copy out strings (args and env) and initialize stack base
  680          */
  681         if (p->p_sysent->sv_copyout_strings)
  682                 stack_base = (*p->p_sysent->sv_copyout_strings)(imgp);
  683         else
  684                 stack_base = exec_copyout_strings(imgp);
  685 
  686         /*
  687          * If custom stack fixup routine present for this process
  688          * let it do the stack setup.
  689          * Else stuff argument count as first item on stack
  690          */
  691         if (p->p_sysent->sv_fixup != NULL)
  692                 (*p->p_sysent->sv_fixup)(&stack_base, imgp);
  693         else
  694                 suword(--stack_base, imgp->args->argc);
  695 
  696         if (args->fdp != NULL) {
  697                 /* Install a brand new file descriptor table. */
  698                 fdinstall_remapped(td, args->fdp);
  699                 args->fdp = NULL;
  700         } else {
  701                 /*
  702                  * Keep on using the existing file descriptor table. For
  703                  * security and other reasons, the file descriptor table
  704                  * cannot be shared after an exec.
  705                  */
  706                 fdunshare(td);
  707                 /* close files on exec */
  708                 fdcloseexec(td);
  709         }
  710 
  711         /*
  712          * Malloc things before we need locks.
  713          */
  714         i = imgp->args->begin_envv - imgp->args->begin_argv;
  715         /* Cache arguments if they fit inside our allowance */
  716         if (ps_arg_cache_limit >= i + sizeof(struct pargs)) {
  717                 newargs = pargs_alloc(i);
  718                 bcopy(imgp->args->begin_argv, newargs->ar_args, i);
  719         }
  720 
  721         /*
  722          * For security and other reasons, signal handlers cannot
  723          * be shared after an exec. The new process gets a copy of the old
  724          * handlers. In execsigs(), the new process will have its signals
  725          * reset.
  726          */
  727         if (sigacts_shared(p->p_sigacts)) {
  728                 oldsigacts = p->p_sigacts;
  729                 newsigacts = sigacts_alloc();
  730                 sigacts_copy(newsigacts, oldsigacts);
  731         }
  732 
  733         vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
  734 
  735         PROC_LOCK(p);
  736         if (oldsigacts)
  737                 p->p_sigacts = newsigacts;
  738         /* Stop profiling */
  739         stopprofclock(p);
  740 
  741         /* reset caught signals */
  742         execsigs(p);
  743 
  744         /* name this process - nameiexec(p, ndp) */
  745         bzero(p->p_comm, sizeof(p->p_comm));
  746         if (args->fname)
  747                 bcopy(nd.ni_cnd.cn_nameptr, p->p_comm,
  748                     min(nd.ni_cnd.cn_namelen, MAXCOMLEN));
  749         else if (vn_commname(newtextvp, p->p_comm, sizeof(p->p_comm)) != 0)
  750                 bcopy(fexecv_proc_title, p->p_comm, sizeof(fexecv_proc_title));
  751         bcopy(p->p_comm, td->td_name, sizeof(td->td_name));
  752 #ifdef KTR
  753         sched_clear_tdname(td);
  754 #endif
  755 
  756         /*
  757          * mark as execed, wakeup the process that vforked (if any) and tell
  758          * it that it now has its own resources back
  759          */
  760         p->p_flag |= P_EXEC;
  761         if ((p->p_flag2 & P2_NOTRACE_EXEC) == 0)
  762                 p->p_flag2 &= ~P2_NOTRACE;
  763         if ((p->p_flag2 & P2_STKGAP_DISABLE_EXEC) == 0)
  764                 p->p_flag2 &= ~P2_STKGAP_DISABLE;
  765         if (p->p_flag & P_PPWAIT) {
  766                 p->p_flag &= ~(P_PPWAIT | P_PPTRACE);
  767                 cv_broadcast(&p->p_pwait);
  768                 /* STOPs are no longer ignored, arrange for AST */
  769                 signotify(td);
  770         }
  771 
  772         /*
  773          * Implement image setuid/setgid installation.
  774          */
  775         if (imgp->credential_setid) {
  776                 /*
  777                  * Turn off syscall tracing for set-id programs, except for
  778                  * root.  Record any set-id flags first to make sure that
  779                  * we do not regain any tracing during a possible block.
  780                  */
  781                 setsugid(p);
  782 
  783 #ifdef KTRACE
  784                 if (p->p_tracecred != NULL &&
  785                     priv_check_cred(p->p_tracecred, PRIV_DEBUG_DIFFCRED, 0))
  786                         ktrprocexec(p, &tracecred, &tracevp);
  787 #endif
  788                 /*
  789                  * Close any file descriptors 0..2 that reference procfs,
  790                  * then make sure file descriptors 0..2 are in use.
  791                  *
  792                  * Both fdsetugidsafety() and fdcheckstd() may call functions
  793                  * taking sleepable locks, so temporarily drop our locks.
  794                  */
  795                 PROC_UNLOCK(p);
  796                 VOP_UNLOCK(imgp->vp, 0);
  797                 fdsetugidsafety(td);
  798                 error = fdcheckstd(td);
  799                 vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
  800                 if (error != 0)
  801                         goto exec_fail_dealloc;
  802                 PROC_LOCK(p);
  803 #ifdef MAC
  804                 if (will_transition) {
  805                         mac_vnode_execve_transition(oldcred, imgp->newcred,
  806                             imgp->vp, interpvplabel, imgp);
  807                 }
  808 #endif
  809         } else {
  810                 if (oldcred->cr_uid == oldcred->cr_ruid &&
  811                     oldcred->cr_gid == oldcred->cr_rgid)
  812                         p->p_flag &= ~P_SUGID;
  813         }
  814         /*
  815          * Set the new credentials.
  816          */
  817         if (imgp->newcred != NULL) {
  818                 proc_set_cred(p, imgp->newcred);
  819                 crfree(oldcred);
  820                 oldcred = NULL;
  821         }
  822 
  823         /*
  824          * Store the vp for use in procfs.  This vnode was referenced by namei
  825          * or fgetvp_exec.
  826          */
  827         oldtextvp = p->p_textvp;
  828         p->p_textvp = newtextvp;
  829 
  830 #ifdef KDTRACE_HOOKS
  831         /*
  832          * Tell the DTrace fasttrap provider about the exec if it
  833          * has declared an interest.
  834          */
  835         if (dtrace_fasttrap_exec)
  836                 dtrace_fasttrap_exec(p);
  837 #endif
  838 
  839         /*
  840          * Notify others that we exec'd, and clear the P_INEXEC flag
  841          * as we're now a bona fide freshly-execed process.
  842          */
  843         KNOTE_LOCKED(p->p_klist, NOTE_EXEC);
  844         p->p_flag &= ~P_INEXEC;
  845 
  846         /* clear "fork but no exec" flag, as we _are_ execing */
  847         p->p_acflag &= ~AFORK;
  848 
  849         /*
  850          * Free any previous argument cache and replace it with
  851          * the new argument cache, if any.
  852          */
  853         oldargs = p->p_args;
  854         p->p_args = newargs;
  855         newargs = NULL;
  856 
  857 #ifdef  HWPMC_HOOKS
  858         /*
  859          * Check if system-wide sampling is in effect or if the
  860          * current process is using PMCs.  If so, do exec() time
  861          * processing.  This processing needs to happen AFTER the
  862          * P_INEXEC flag is cleared.
  863          *
  864          * The proc lock needs to be released before taking the PMC
  865          * SX.
  866          */
  867         if (PMC_SYSTEM_SAMPLING_ACTIVE() || PMC_PROC_IS_USING_PMCS(p)) {
  868                 PROC_UNLOCK(p);
  869                 VOP_UNLOCK(imgp->vp, 0);
  870                 pe.pm_credentialschanged = credential_changing;
  871                 pe.pm_entryaddr = imgp->entry_addr;
  872 
  873                 PMC_CALL_HOOK_X(td, PMC_FN_PROCESS_EXEC, (void *) &pe);
  874                 vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
  875         } else
  876                 PROC_UNLOCK(p);
  877 #else  /* !HWPMC_HOOKS */
  878         PROC_UNLOCK(p);
  879 #endif
  880 
  881         /* Set values passed into the program in registers. */
  882         if (p->p_sysent->sv_setregs)
  883                 (*p->p_sysent->sv_setregs)(td, imgp, 
  884                     (u_long)(uintptr_t)stack_base);
  885         else
  886                 exec_setregs(td, imgp, (u_long)(uintptr_t)stack_base);
  887 
  888         vfs_mark_atime(imgp->vp, td->td_ucred);
  889 
  890         SDT_PROBE1(proc, , , exec__success, args->fname);
  891 
  892 exec_fail_dealloc:
  893         if (error != 0) {
  894                 p->p_osrel = orig_osrel;
  895         }
  896 
  897         if (imgp->firstpage != NULL)
  898                 exec_unmap_first_page(imgp);
  899 
  900         if (imgp->vp != NULL) {
  901                 if (args->fname)
  902                         NDFREE(&nd, NDF_ONLY_PNBUF);
  903                 if (imgp->opened)
  904                         VOP_CLOSE(imgp->vp, FREAD, td->td_ucred, td);
  905                 if (error != 0)
  906                         vput(imgp->vp);
  907                 else
  908                         VOP_UNLOCK(imgp->vp, 0);
  909         }
  910 
  911         if (imgp->object != NULL)
  912                 vm_object_deallocate(imgp->object);
  913 
  914         free(imgp->freepath, M_TEMP);
  915 
  916         if (error == 0) {
  917                 PROC_LOCK(p);
  918                 if (p->p_ptevents & PTRACE_EXEC)
  919                         td->td_dbgflags |= TDB_EXEC;
  920                 PROC_UNLOCK(p);
  921 
  922                 /*
  923                  * Stop the process here if its stop event mask has
  924                  * the S_EXEC bit set.
  925                  */
  926                 STOPEVENT(p, S_EXEC, 0);
  927         } else {
  928 exec_fail:
  929                 /* we're done here, clear P_INEXEC */
  930                 PROC_LOCK(p);
  931                 p->p_flag &= ~P_INEXEC;
  932                 PROC_UNLOCK(p);
  933 
  934                 SDT_PROBE1(proc, , , exec__failure, error);
  935         }
  936 
  937         if (imgp->newcred != NULL && oldcred != NULL)
  938                 crfree(imgp->newcred);
  939 
  940 #ifdef MAC
  941         mac_execve_exit(imgp);
  942         mac_execve_interpreter_exit(interpvplabel);
  943 #endif
  944         exec_free_args(args);
  945 
  946         /*
  947          * Handle deferred decrement of ref counts.
  948          */
  949         if (oldtextvp != NULL)
  950                 vrele(oldtextvp);
  951 #ifdef KTRACE
  952         if (tracevp != NULL)
  953                 vrele(tracevp);
  954         if (tracecred != NULL)
  955                 crfree(tracecred);
  956 #endif
  957         pargs_drop(oldargs);
  958         pargs_drop(newargs);
  959         if (oldsigacts != NULL)
  960                 sigacts_free(oldsigacts);
  961         if (euip != NULL)
  962                 uifree(euip);
  963 
  964         if (error && imgp->vmspace_destroyed) {
  965                 /* sorry, no more process anymore. exit gracefully */
  966                 exec_cleanup(td, oldvmspace);
  967                 exit1(td, 0, SIGABRT);
  968                 /* NOT REACHED */
  969         }
  970 
  971 #ifdef KTRACE
  972         if (error == 0)
  973                 ktrprocctor(p);
  974 #endif
  975 
  976         return (error);
  977 }
  978 
  979 void
  980 exec_cleanup(struct thread *td, struct vmspace *oldvmspace)
  981 {
  982         if ((td->td_pflags & TDP_EXECVMSPC) != 0) {
  983                 KASSERT(td->td_proc->p_vmspace != oldvmspace,
  984                     ("oldvmspace still used"));
  985                 vmspace_free(oldvmspace);
  986                 td->td_pflags &= ~TDP_EXECVMSPC;
  987         }
  988 }
  989 
  990 int
  991 exec_map_first_page(imgp)
  992         struct image_params *imgp;
  993 {
  994         int rv, i, after, initial_pagein;
  995         vm_page_t ma[VM_INITIAL_PAGEIN];
  996         vm_object_t object;
  997 
  998         if (imgp->firstpage != NULL)
  999                 exec_unmap_first_page(imgp);
 1000 
 1001         object = imgp->vp->v_object;
 1002         if (object == NULL)
 1003                 return (EACCES);
 1004         VM_OBJECT_WLOCK(object);
 1005 #if VM_NRESERVLEVEL > 0
 1006         vm_object_color(object, 0);
 1007 #endif
 1008         ma[0] = vm_page_grab(object, 0, VM_ALLOC_NORMAL | VM_ALLOC_NOBUSY);
 1009         if (ma[0]->valid != VM_PAGE_BITS_ALL) {
 1010                 vm_page_xbusy(ma[0]);
 1011                 if (!vm_pager_has_page(object, 0, NULL, &after)) {
 1012                         vm_page_lock(ma[0]);
 1013                         vm_page_free(ma[0]);
 1014                         vm_page_unlock(ma[0]);
 1015                         VM_OBJECT_WUNLOCK(object);
 1016                         return (EIO);
 1017                 }
 1018                 initial_pagein = min(after, VM_INITIAL_PAGEIN);
 1019                 KASSERT(initial_pagein <= object->size,
 1020                     ("%s: initial_pagein %d object->size %ju",
 1021                     __func__, initial_pagein, (uintmax_t )object->size));
 1022                 for (i = 1; i < initial_pagein; i++) {
 1023                         if ((ma[i] = vm_page_next(ma[i - 1])) != NULL) {
 1024                                 if (ma[i]->valid)
 1025                                         break;
 1026                                 if (!vm_page_tryxbusy(ma[i]))
 1027                                         break;
 1028                         } else {
 1029                                 ma[i] = vm_page_alloc(object, i,
 1030                                     VM_ALLOC_NORMAL);
 1031                                 if (ma[i] == NULL)
 1032                                         break;
 1033                         }
 1034                 }
 1035                 initial_pagein = i;
 1036                 rv = vm_pager_get_pages(object, ma, initial_pagein, NULL, NULL);
 1037                 if (rv != VM_PAGER_OK) {
 1038                         for (i = 0; i < initial_pagein; i++) {
 1039                                 vm_page_lock(ma[i]);
 1040                                 vm_page_free(ma[i]);
 1041                                 vm_page_unlock(ma[i]);
 1042                         }
 1043                         VM_OBJECT_WUNLOCK(object);
 1044                         return (EIO);
 1045                 }
 1046                 vm_page_xunbusy(ma[0]);
 1047                 for (i = 1; i < initial_pagein; i++)
 1048                         vm_page_readahead_finish(ma[i]);
 1049         }
 1050         vm_page_lock(ma[0]);
 1051         vm_page_hold(ma[0]);
 1052         vm_page_activate(ma[0]);
 1053         vm_page_unlock(ma[0]);
 1054         VM_OBJECT_WUNLOCK(object);
 1055 
 1056         imgp->firstpage = sf_buf_alloc(ma[0], 0);
 1057         imgp->image_header = (char *)sf_buf_kva(imgp->firstpage);
 1058 
 1059         return (0);
 1060 }
 1061 
 1062 void
 1063 exec_unmap_first_page(struct image_params *imgp)
 1064 {
 1065         vm_page_t m;
 1066 
 1067         if (imgp->firstpage != NULL) {
 1068                 m = sf_buf_page(imgp->firstpage);
 1069                 sf_buf_free(imgp->firstpage);
 1070                 imgp->firstpage = NULL;
 1071                 vm_page_lock(m);
 1072                 vm_page_unhold(m);
 1073                 vm_page_unlock(m);
 1074         }
 1075 }
 1076 
 1077 /*
 1078  * Destroy old address space, and allocate a new stack.
 1079  *      The new stack is only sgrowsiz large because it is grown
 1080  *      automatically on a page fault.
 1081  */
 1082 int
 1083 exec_new_vmspace(struct image_params *imgp, struct sysentvec *sv)
 1084 {
 1085         int error;
 1086         struct proc *p = imgp->proc;
 1087         struct vmspace *vmspace = p->p_vmspace;
 1088         vm_object_t obj;
 1089         struct rlimit rlim_stack;
 1090         vm_offset_t sv_minuser, stack_addr;
 1091         vm_map_t map;
 1092         u_long ssiz;
 1093 
 1094         imgp->vmspace_destroyed = 1;
 1095         imgp->sysent = sv;
 1096 
 1097         /* May be called with Giant held */
 1098         EVENTHANDLER_DIRECT_INVOKE(process_exec, p, imgp);
 1099 
 1100         /*
 1101          * Blow away entire process VM, if address space not shared,
 1102          * otherwise, create a new VM space so that other threads are
 1103          * not disrupted
 1104          */
 1105         map = &vmspace->vm_map;
 1106         if (map_at_zero)
 1107                 sv_minuser = sv->sv_minuser;
 1108         else
 1109                 sv_minuser = MAX(sv->sv_minuser, PAGE_SIZE);
 1110         if (vmspace->vm_refcnt == 1 && vm_map_min(map) == sv_minuser &&
 1111             vm_map_max(map) == sv->sv_maxuser) {
 1112                 shmexit(vmspace);
 1113                 pmap_remove_pages(vmspace_pmap(vmspace));
 1114                 vm_map_remove(map, vm_map_min(map), vm_map_max(map));
 1115                 /* An exec terminates mlockall(MCL_FUTURE). */
 1116                 vm_map_lock(map);
 1117                 vm_map_modflags(map, 0, MAP_WIREFUTURE);
 1118                 vm_map_unlock(map);
 1119         } else {
 1120                 error = vmspace_exec(p, sv_minuser, sv->sv_maxuser);
 1121                 if (error)
 1122                         return (error);
 1123                 vmspace = p->p_vmspace;
 1124                 map = &vmspace->vm_map;
 1125         }
 1126 
 1127         /* Map a shared page */
 1128         obj = sv->sv_shared_page_obj;
 1129         if (obj != NULL) {
 1130                 vm_object_reference(obj);
 1131                 error = vm_map_fixed(map, obj, 0,
 1132                     sv->sv_shared_page_base, sv->sv_shared_page_len,
 1133                     VM_PROT_READ | VM_PROT_EXECUTE,
 1134                     VM_PROT_READ | VM_PROT_EXECUTE,
 1135                     MAP_INHERIT_SHARE | MAP_ACC_NO_CHARGE);
 1136                 if (error != KERN_SUCCESS) {
 1137                         vm_object_deallocate(obj);
 1138                         return (vm_mmap_to_errno(error));
 1139                 }
 1140         }
 1141 
 1142         /* Allocate a new stack */
 1143         if (imgp->stack_sz != 0) {
 1144                 ssiz = trunc_page(imgp->stack_sz);
 1145                 PROC_LOCK(p);
 1146                 lim_rlimit_proc(p, RLIMIT_STACK, &rlim_stack);
 1147                 PROC_UNLOCK(p);
 1148                 if (ssiz > rlim_stack.rlim_max)
 1149                         ssiz = rlim_stack.rlim_max;
 1150                 if (ssiz > rlim_stack.rlim_cur) {
 1151                         rlim_stack.rlim_cur = ssiz;
 1152                         kern_setrlimit(curthread, RLIMIT_STACK, &rlim_stack);
 1153                 }
 1154         } else if (sv->sv_maxssiz != NULL) {
 1155                 ssiz = *sv->sv_maxssiz;
 1156         } else {
 1157                 ssiz = maxssiz;
 1158         }
 1159         stack_addr = sv->sv_usrstack - ssiz;
 1160         error = vm_map_stack(map, stack_addr, (vm_size_t)ssiz,
 1161             obj != NULL && imgp->stack_prot != 0 ? imgp->stack_prot :
 1162             sv->sv_stackprot, VM_PROT_ALL, MAP_STACK_GROWS_DOWN);
 1163         if (error != KERN_SUCCESS)
 1164                 return (vm_mmap_to_errno(error));
 1165 
 1166         /*
 1167          * vm_ssize and vm_maxsaddr are somewhat antiquated concepts, but they
 1168          * are still used to enforce the stack rlimit on the process stack.
 1169          */
 1170         vmspace->vm_ssize = sgrowsiz >> PAGE_SHIFT;
 1171         vmspace->vm_maxsaddr = (char *)stack_addr;
 1172 
 1173         return (0);
 1174 }
 1175 
 1176 /*
 1177  * Copy out argument and environment strings from the old process address
 1178  * space into the temporary string buffer.
 1179  */
 1180 int
 1181 exec_copyin_args(struct image_args *args, char *fname,
 1182     enum uio_seg segflg, char **argv, char **envv)
 1183 {
 1184         u_long argp, envp;
 1185         int error;
 1186         size_t length;
 1187 
 1188         bzero(args, sizeof(*args));
 1189         if (argv == NULL)
 1190                 return (EFAULT);
 1191 
 1192         /*
 1193          * Allocate demand-paged memory for the file name, argument, and
 1194          * environment strings.
 1195          */
 1196         error = exec_alloc_args(args);
 1197         if (error != 0)
 1198                 return (error);
 1199 
 1200         /*
 1201          * Copy the file name.
 1202          */
 1203         if (fname != NULL) {
 1204                 args->fname = args->buf;
 1205                 error = (segflg == UIO_SYSSPACE) ?
 1206                     copystr(fname, args->fname, PATH_MAX, &length) :
 1207                     copyinstr(fname, args->fname, PATH_MAX, &length);
 1208                 if (error != 0)
 1209                         goto err_exit;
 1210         } else
 1211                 length = 0;
 1212 
 1213         args->begin_argv = args->buf + length;
 1214         args->endp = args->begin_argv;
 1215         args->stringspace = ARG_MAX;
 1216 
 1217         /*
 1218          * extract arguments first
 1219          */
 1220         for (;;) {
 1221                 error = fueword(argv++, &argp);
 1222                 if (error == -1) {
 1223                         error = EFAULT;
 1224                         goto err_exit;
 1225                 }
 1226                 if (argp == 0)
 1227                         break;
 1228                 error = copyinstr((void *)(uintptr_t)argp, args->endp,
 1229                     args->stringspace, &length);
 1230                 if (error != 0) {
 1231                         if (error == ENAMETOOLONG) 
 1232                                 error = E2BIG;
 1233                         goto err_exit;
 1234                 }
 1235                 args->stringspace -= length;
 1236                 args->endp += length;
 1237                 args->argc++;
 1238         }
 1239 
 1240         args->begin_envv = args->endp;
 1241 
 1242         /*
 1243          * extract environment strings
 1244          */
 1245         if (envv) {
 1246                 for (;;) {
 1247                         error = fueword(envv++, &envp);
 1248                         if (error == -1) {
 1249                                 error = EFAULT;
 1250                                 goto err_exit;
 1251                         }
 1252                         if (envp == 0)
 1253                                 break;
 1254                         error = copyinstr((void *)(uintptr_t)envp,
 1255                             args->endp, args->stringspace, &length);
 1256                         if (error != 0) {
 1257                                 if (error == ENAMETOOLONG)
 1258                                         error = E2BIG;
 1259                                 goto err_exit;
 1260                         }
 1261                         args->stringspace -= length;
 1262                         args->endp += length;
 1263                         args->envc++;
 1264                 }
 1265         }
 1266 
 1267         return (0);
 1268 
 1269 err_exit:
 1270         exec_free_args(args);
 1271         return (error);
 1272 }
 1273 
 1274 int
 1275 exec_copyin_data_fds(struct thread *td, struct image_args *args,
 1276     const void *data, size_t datalen, const int *fds, size_t fdslen)
 1277 {
 1278         struct filedesc *ofdp;
 1279         const char *p;
 1280         int *kfds;
 1281         int error;
 1282 
 1283         memset(args, '\0', sizeof(*args));
 1284         ofdp = td->td_proc->p_fd;
 1285         if (datalen >= ARG_MAX || fdslen > ofdp->fd_lastfile + 1)
 1286                 return (E2BIG);
 1287         error = exec_alloc_args(args);
 1288         if (error != 0)
 1289                 return (error);
 1290 
 1291         args->begin_argv = args->buf;
 1292         args->stringspace = ARG_MAX;
 1293 
 1294         if (datalen > 0) {
 1295                 /*
 1296                  * Argument buffer has been provided. Copy it into the
 1297                  * kernel as a single string and add a terminating null
 1298                  * byte.
 1299                  */
 1300                 error = copyin(data, args->begin_argv, datalen);
 1301                 if (error != 0)
 1302                         goto err_exit;
 1303                 args->begin_argv[datalen] = '\0';
 1304                 args->endp = args->begin_argv + datalen + 1;
 1305                 args->stringspace -= datalen + 1;
 1306 
 1307                 /*
 1308                  * Traditional argument counting. Count the number of
 1309                  * null bytes.
 1310                  */
 1311                 for (p = args->begin_argv; p < args->endp; ++p)
 1312                         if (*p == '\0')
 1313                                 ++args->argc;
 1314         } else {
 1315                 /* No argument buffer provided. */
 1316                 args->endp = args->begin_argv;
 1317         }
 1318         /* There are no environment variables. */
 1319         args->begin_envv = args->endp;
 1320 
 1321         /* Create new file descriptor table. */
 1322         kfds = malloc(fdslen * sizeof(int), M_TEMP, M_WAITOK);
 1323         error = copyin(fds, kfds, fdslen * sizeof(int));
 1324         if (error != 0) {
 1325                 free(kfds, M_TEMP);
 1326                 goto err_exit;
 1327         }
 1328         error = fdcopy_remapped(ofdp, kfds, fdslen, &args->fdp);
 1329         free(kfds, M_TEMP);
 1330         if (error != 0)
 1331                 goto err_exit;
 1332 
 1333         return (0);
 1334 err_exit:
 1335         exec_free_args(args);
 1336         return (error);
 1337 }
 1338 
 1339 struct exec_args_kva {
 1340         vm_offset_t addr;
 1341         u_int gen;
 1342         SLIST_ENTRY(exec_args_kva) next;
 1343 };
 1344 
 1345 static DPCPU_DEFINE(struct exec_args_kva *, exec_args_kva);
 1346 
 1347 static SLIST_HEAD(, exec_args_kva) exec_args_kva_freelist;
 1348 static struct mtx exec_args_kva_mtx;
 1349 static u_int exec_args_gen;
 1350 
 1351 static void
 1352 exec_prealloc_args_kva(void *arg __unused)
 1353 {
 1354         struct exec_args_kva *argkva;
 1355         u_int i;
 1356 
 1357         SLIST_INIT(&exec_args_kva_freelist);
 1358         mtx_init(&exec_args_kva_mtx, "exec args kva", NULL, MTX_DEF);
 1359         for (i = 0; i < exec_map_entries; i++) {
 1360                 argkva = malloc(sizeof(*argkva), M_PARGS, M_WAITOK);
 1361                 argkva->addr = kmap_alloc_wait(exec_map, exec_map_entry_size);
 1362                 argkva->gen = exec_args_gen;
 1363                 SLIST_INSERT_HEAD(&exec_args_kva_freelist, argkva, next);
 1364         }
 1365 }
 1366 SYSINIT(exec_args_kva, SI_SUB_EXEC, SI_ORDER_ANY, exec_prealloc_args_kva, NULL);
 1367 
 1368 static vm_offset_t
 1369 exec_alloc_args_kva(void **cookie)
 1370 {
 1371         struct exec_args_kva *argkva;
 1372 
 1373         argkva = (void *)atomic_readandclear_ptr(
 1374             (uintptr_t *)DPCPU_PTR(exec_args_kva));
 1375         if (argkva == NULL) {
 1376                 mtx_lock(&exec_args_kva_mtx);
 1377                 while ((argkva = SLIST_FIRST(&exec_args_kva_freelist)) == NULL)
 1378                         (void)mtx_sleep(&exec_args_kva_freelist,
 1379                             &exec_args_kva_mtx, 0, "execkva", 0);
 1380                 SLIST_REMOVE_HEAD(&exec_args_kva_freelist, next);
 1381                 mtx_unlock(&exec_args_kva_mtx);
 1382         }
 1383         *(struct exec_args_kva **)cookie = argkva;
 1384         return (argkva->addr);
 1385 }
 1386 
 1387 static void
 1388 exec_release_args_kva(struct exec_args_kva *argkva, u_int gen)
 1389 {
 1390         vm_offset_t base;
 1391 
 1392         base = argkva->addr;
 1393         if (argkva->gen != gen) {
 1394                 vm_map_madvise(exec_map, base, base + exec_map_entry_size,
 1395                     MADV_FREE);
 1396                 argkva->gen = gen;
 1397         }
 1398         if (!atomic_cmpset_ptr((uintptr_t *)DPCPU_PTR(exec_args_kva),
 1399             (uintptr_t)NULL, (uintptr_t)argkva)) {
 1400                 mtx_lock(&exec_args_kva_mtx);
 1401                 SLIST_INSERT_HEAD(&exec_args_kva_freelist, argkva, next);
 1402                 wakeup_one(&exec_args_kva_freelist);
 1403                 mtx_unlock(&exec_args_kva_mtx);
 1404         }
 1405 }
 1406 
 1407 static void
 1408 exec_free_args_kva(void *cookie)
 1409 {
 1410 
 1411         exec_release_args_kva(cookie, exec_args_gen);
 1412 }
 1413 
 1414 static void
 1415 exec_args_kva_lowmem(void *arg __unused)
 1416 {
 1417         SLIST_HEAD(, exec_args_kva) head;
 1418         struct exec_args_kva *argkva;
 1419         u_int gen;
 1420         int i;
 1421 
 1422         gen = atomic_fetchadd_int(&exec_args_gen, 1) + 1;
 1423 
 1424         /*
 1425          * Force an madvise of each KVA range. Any currently allocated ranges
 1426          * will have MADV_FREE applied once they are freed.
 1427          */
 1428         SLIST_INIT(&head);
 1429         mtx_lock(&exec_args_kva_mtx);
 1430         SLIST_SWAP(&head, &exec_args_kva_freelist, exec_args_kva);
 1431         mtx_unlock(&exec_args_kva_mtx);
 1432         while ((argkva = SLIST_FIRST(&head)) != NULL) {
 1433                 SLIST_REMOVE_HEAD(&head, next);
 1434                 exec_release_args_kva(argkva, gen);
 1435         }
 1436 
 1437         CPU_FOREACH(i) {
 1438                 argkva = (void *)atomic_readandclear_ptr(
 1439                     (uintptr_t *)DPCPU_ID_PTR(i, exec_args_kva));
 1440                 if (argkva != NULL)
 1441                         exec_release_args_kva(argkva, gen);
 1442         }
 1443 }
 1444 EVENTHANDLER_DEFINE(vm_lowmem, exec_args_kva_lowmem, NULL,
 1445     EVENTHANDLER_PRI_ANY);
 1446 
 1447 /*
 1448  * Allocate temporary demand-paged, zero-filled memory for the file name,
 1449  * argument, and environment strings.
 1450  */
 1451 int
 1452 exec_alloc_args(struct image_args *args)
 1453 {
 1454 
 1455         args->buf = (char *)exec_alloc_args_kva(&args->bufkva);
 1456         return (0);
 1457 }
 1458 
 1459 void
 1460 exec_free_args(struct image_args *args)
 1461 {
 1462 
 1463         if (args->buf != NULL) {
 1464                 exec_free_args_kva(args->bufkva);
 1465                 args->buf = NULL;
 1466         }
 1467         if (args->fname_buf != NULL) {
 1468                 free(args->fname_buf, M_TEMP);
 1469                 args->fname_buf = NULL;
 1470         }
 1471         if (args->fdp != NULL)
 1472                 fdescfree_remapped(args->fdp);
 1473 }
 1474 
 1475 /*
 1476  * Copy strings out to the new process address space, constructing new arg
 1477  * and env vector tables. Return a pointer to the base so that it can be used
 1478  * as the initial stack pointer.
 1479  */
 1480 register_t *
 1481 exec_copyout_strings(struct image_params *imgp)
 1482 {
 1483         int argc, envc;
 1484         char **vectp;
 1485         char *stringp;
 1486         uintptr_t destp;
 1487         register_t *stack_base;
 1488         struct ps_strings *arginfo;
 1489         struct proc *p;
 1490         size_t execpath_len;
 1491         int szsigcode, szps;
 1492         char canary[sizeof(long) * 8];
 1493 
 1494         szps = sizeof(pagesizes[0]) * MAXPAGESIZES;
 1495         /*
 1496          * Calculate string base and vector table pointers.
 1497          * Also deal with signal trampoline code for this exec type.
 1498          */
 1499         if (imgp->execpath != NULL && imgp->auxargs != NULL)
 1500                 execpath_len = strlen(imgp->execpath) + 1;
 1501         else
 1502                 execpath_len = 0;
 1503         p = imgp->proc;
 1504         szsigcode = 0;
 1505         arginfo = (struct ps_strings *)p->p_sysent->sv_psstrings;
 1506         if (p->p_sysent->sv_sigcode_base == 0) {
 1507                 if (p->p_sysent->sv_szsigcode != NULL)
 1508                         szsigcode = *(p->p_sysent->sv_szsigcode);
 1509         }
 1510         destp = (uintptr_t)arginfo;
 1511 
 1512         /*
 1513          * install sigcode
 1514          */
 1515         if (szsigcode != 0) {
 1516                 destp -= szsigcode;
 1517                 destp = rounddown2(destp, sizeof(void *));
 1518                 copyout(p->p_sysent->sv_sigcode, (void *)destp, szsigcode);
 1519         }
 1520 
 1521         /*
 1522          * Copy the image path for the rtld.
 1523          */
 1524         if (execpath_len != 0) {
 1525                 destp -= execpath_len;
 1526                 destp = rounddown2(destp, sizeof(void *));
 1527                 imgp->execpathp = destp;
 1528                 copyout(imgp->execpath, (void *)destp, execpath_len);
 1529         }
 1530 
 1531         /*
 1532          * Prepare the canary for SSP.
 1533          */
 1534         arc4rand(canary, sizeof(canary), 0);
 1535         destp -= sizeof(canary);
 1536         imgp->canary = destp;
 1537         copyout(canary, (void *)destp, sizeof(canary));
 1538         imgp->canarylen = sizeof(canary);
 1539 
 1540         /*
 1541          * Prepare the pagesizes array.
 1542          */
 1543         destp -= szps;
 1544         destp = rounddown2(destp, sizeof(void *));
 1545         imgp->pagesizes = destp;
 1546         copyout(pagesizes, (void *)destp, szps);
 1547         imgp->pagesizeslen = szps;
 1548 
 1549         destp -= ARG_MAX - imgp->args->stringspace;
 1550         destp = rounddown2(destp, sizeof(void *));
 1551 
 1552         vectp = (char **)destp;
 1553         if (imgp->auxargs) {
 1554                 /*
 1555                  * Allocate room on the stack for the ELF auxargs
 1556                  * array.  It has up to AT_COUNT entries.
 1557                  */
 1558                 vectp -= howmany(AT_COUNT * sizeof(Elf_Auxinfo),
 1559                     sizeof(*vectp));
 1560         }
 1561 
 1562         /*
 1563          * Allocate room for the argv[] and env vectors including the
 1564          * terminating NULL pointers.
 1565          */
 1566         vectp -= imgp->args->argc + 1 + imgp->args->envc + 1;
 1567 
 1568         /*
 1569          * vectp also becomes our initial stack base
 1570          */
 1571         stack_base = (register_t *)vectp;
 1572 
 1573         stringp = imgp->args->begin_argv;
 1574         argc = imgp->args->argc;
 1575         envc = imgp->args->envc;
 1576 
 1577         /*
 1578          * Copy out strings - arguments and environment.
 1579          */
 1580         copyout(stringp, (void *)destp, ARG_MAX - imgp->args->stringspace);
 1581 
 1582         /*
 1583          * Fill in "ps_strings" struct for ps, w, etc.
 1584          */
 1585         suword(&arginfo->ps_argvstr, (long)(intptr_t)vectp);
 1586         suword32(&arginfo->ps_nargvstr, argc);
 1587 
 1588         /*
 1589          * Fill in argument portion of vector table.
 1590          */
 1591         for (; argc > 0; --argc) {
 1592                 suword(vectp++, (long)(intptr_t)destp);
 1593                 while (*stringp++ != 0)
 1594                         destp++;
 1595                 destp++;
 1596         }
 1597 
 1598         /* a null vector table pointer separates the argp's from the envp's */
 1599         suword(vectp++, 0);
 1600 
 1601         suword(&arginfo->ps_envstr, (long)(intptr_t)vectp);
 1602         suword32(&arginfo->ps_nenvstr, envc);
 1603 
 1604         /*
 1605          * Fill in environment portion of vector table.
 1606          */
 1607         for (; envc > 0; --envc) {
 1608                 suword(vectp++, (long)(intptr_t)destp);
 1609                 while (*stringp++ != 0)
 1610                         destp++;
 1611                 destp++;
 1612         }
 1613 
 1614         /* end of vector table is a null pointer */
 1615         suword(vectp, 0);
 1616 
 1617         return (stack_base);
 1618 }
 1619 
 1620 /*
 1621  * Check permissions of file to execute.
 1622  *      Called with imgp->vp locked.
 1623  *      Return 0 for success or error code on failure.
 1624  */
 1625 int
 1626 exec_check_permissions(struct image_params *imgp)
 1627 {
 1628         struct vnode *vp = imgp->vp;
 1629         struct vattr *attr = imgp->attr;
 1630         struct thread *td;
 1631         int error, writecount;
 1632 
 1633         td = curthread;
 1634 
 1635         /* Get file attributes */
 1636         error = VOP_GETATTR(vp, attr, td->td_ucred);
 1637         if (error)
 1638                 return (error);
 1639 
 1640 #ifdef MAC
 1641         error = mac_vnode_check_exec(td->td_ucred, imgp->vp, imgp);
 1642         if (error)
 1643                 return (error);
 1644 #endif
 1645 
 1646         /*
 1647          * 1) Check if file execution is disabled for the filesystem that
 1648          *    this file resides on.
 1649          * 2) Ensure that at least one execute bit is on. Otherwise, a
 1650          *    privileged user will always succeed, and we don't want this
 1651          *    to happen unless the file really is executable.
 1652          * 3) Ensure that the file is a regular file.
 1653          */
 1654         if ((vp->v_mount->mnt_flag & MNT_NOEXEC) ||
 1655             (attr->va_mode & (S_IXUSR | S_IXGRP | S_IXOTH)) == 0 ||
 1656             (attr->va_type != VREG))
 1657                 return (EACCES);
 1658 
 1659         /*
 1660          * Zero length files can't be exec'd
 1661          */
 1662         if (attr->va_size == 0)
 1663                 return (ENOEXEC);
 1664 
 1665         /*
 1666          *  Check for execute permission to file based on current credentials.
 1667          */
 1668         error = VOP_ACCESS(vp, VEXEC, td->td_ucred, td);
 1669         if (error)
 1670                 return (error);
 1671 
 1672         /*
 1673          * Check number of open-for-writes on the file and deny execution
 1674          * if there are any.
 1675          */
 1676         error = VOP_GET_WRITECOUNT(vp, &writecount);
 1677         if (error != 0)
 1678                 return (error);
 1679         if (writecount != 0)
 1680                 return (ETXTBSY);
 1681 
 1682         /*
 1683          * Call filesystem specific open routine (which does nothing in the
 1684          * general case).
 1685          */
 1686         error = VOP_OPEN(vp, FREAD, td->td_ucred, td, NULL);
 1687         if (error == 0)
 1688                 imgp->opened = 1;
 1689         return (error);
 1690 }
 1691 
 1692 /*
 1693  * Exec handler registration
 1694  */
 1695 int
 1696 exec_register(const struct execsw *execsw_arg)
 1697 {
 1698         const struct execsw **es, **xs, **newexecsw;
 1699         int count = 2;  /* New slot and trailing NULL */
 1700 
 1701         if (execsw)
 1702                 for (es = execsw; *es; es++)
 1703                         count++;
 1704         newexecsw = malloc(count * sizeof(*es), M_TEMP, M_WAITOK);
 1705         xs = newexecsw;
 1706         if (execsw)
 1707                 for (es = execsw; *es; es++)
 1708                         *xs++ = *es;
 1709         *xs++ = execsw_arg;
 1710         *xs = NULL;
 1711         if (execsw)
 1712                 free(execsw, M_TEMP);
 1713         execsw = newexecsw;
 1714         return (0);
 1715 }
 1716 
 1717 int
 1718 exec_unregister(const struct execsw *execsw_arg)
 1719 {
 1720         const struct execsw **es, **xs, **newexecsw;
 1721         int count = 1;
 1722 
 1723         if (execsw == NULL)
 1724                 panic("unregister with no handlers left?\n");
 1725 
 1726         for (es = execsw; *es; es++) {
 1727                 if (*es == execsw_arg)
 1728                         break;
 1729         }
 1730         if (*es == NULL)
 1731                 return (ENOENT);
 1732         for (es = execsw; *es; es++)
 1733                 if (*es != execsw_arg)
 1734                         count++;
 1735         newexecsw = malloc(count * sizeof(*es), M_TEMP, M_WAITOK);
 1736         xs = newexecsw;
 1737         for (es = execsw; *es; es++)
 1738                 if (*es != execsw_arg)
 1739                         *xs++ = *es;
 1740         *xs = NULL;
 1741         if (execsw)
 1742                 free(execsw, M_TEMP);
 1743         execsw = newexecsw;
 1744         return (0);
 1745 }

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