vfs_helper.c

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    1 /*
    2  * (The copyright below applies to ufs_access())
    3  *
    4  * Copyright (c) 1982, 1986, 1989, 1993, 1995
    5  *      The Regents of the University of California.  All rights reserved.
    6  * (c) UNIX System Laboratories, Inc.
    7  * All or some portions of this file are derived from material licensed
    8  * to the University of California by American Telephone and Telegraph
    9  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
   10  * the permission of UNIX System Laboratories, Inc.
   11  *
   12  * Redistribution and use in source and binary forms, with or without
   13  * modification, are permitted provided that the following conditions
   14  * are met:
   15  * 1. Redistributions of source code must retain the above copyright
   16  *    notice, this list of conditions and the following disclaimer.
   17  * 2. Redistributions in binary form must reproduce the above copyright
   18  *    notice, this list of conditions and the following disclaimer in the
   19  *    documentation and/or other materials provided with the distribution.
   20  * 3. Neither the name of the University nor the names of its contributors
   21  *    may be used to endorse or promote products derived from this software
   22  *    without specific prior written permission.
   23  *
   24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   34  * SUCH DAMAGE.
   35  *
   36  * @(#)ufs_vnops.c      8.27 (Berkeley) 5/27/95
   37  * $DragonFly: src/sys/kern/vfs_helper.c,v 1.5 2008/05/25 18:34:46 dillon Exp $
   38  */
   39 
   40 #include "opt_quota.h"
   41 #include "opt_suiddir.h"
   42 
   43 #include <sys/param.h>
   44 #include <sys/systm.h>
   45 #include <sys/conf.h>
   46 #include <sys/kernel.h>
   47 #include <sys/fcntl.h>
   48 #include <sys/stat.h>
   49 #include <sys/mount.h>
   50 #include <sys/unistd.h>
   51 #include <sys/vnode.h>
   52 #include <sys/file.h>           /* XXX */
   53 #include <sys/proc.h>
   54 #include <sys/priv.h>
   55 #include <sys/jail.h>
   56 #include <sys/sysctl.h>
   57 #include <sys/sfbuf.h>
   58 #include <vm/vm_extern.h>
   59 #include <vm/vm_object.h>
   60 #include <vm/vm_page2.h>
   61 
   62 #ifdef LWBUF_IS_OPTIMAL
   63 
   64 static int vm_read_shortcut_enable = 1;
   65 static long vm_read_shortcut_count;
   66 static long vm_read_shortcut_failed;
   67 SYSCTL_INT(_vm, OID_AUTO, read_shortcut_enable, CTLFLAG_RW,
   68           &vm_read_shortcut_enable, 0, "Direct vm_object vop_read shortcut");
   69 SYSCTL_LONG(_vm, OID_AUTO, read_shortcut_count, CTLFLAG_RW,
   70           &vm_read_shortcut_count, 0, "Statistics");
   71 SYSCTL_LONG(_vm, OID_AUTO, read_shortcut_failed, CTLFLAG_RW,
   72           &vm_read_shortcut_failed, 0, "Statistics");
   73 
   74 #endif
   75 
   76 /*
   77  * vop_helper_access()
   78  *
   79  *      Provide standard UNIX semanics for VOP_ACCESS, but without the quota
   80  *      code.  This procedure was basically pulled out of UFS.
   81  */
   82 int
   83 vop_helper_access(struct vop_access_args *ap, uid_t ino_uid, gid_t ino_gid,
   84                   mode_t ino_mode, u_int32_t ino_flags)
   85 {
   86         struct vnode *vp = ap->a_vp;
   87         struct ucred *cred = ap->a_cred;
   88         mode_t mask, mode = ap->a_mode;
   89         gid_t *gp;
   90         int i;
   91         uid_t proc_uid;
   92         gid_t proc_gid;
   93 
   94         if (ap->a_flags & AT_EACCESS) {
   95                 proc_uid = cred->cr_uid;
   96                 proc_gid = cred->cr_gid;
   97         } else {
   98                 proc_uid = cred->cr_ruid;
   99                 proc_gid = cred->cr_rgid;
  100         }
  101 
  102         /*
  103          * Disallow write attempts on read-only filesystems;
  104          * unless the file is a socket, fifo, or a block or
  105          * character device resident on the filesystem.
  106          */
  107         if (mode & VWRITE) {
  108                 switch (vp->v_type) {
  109                 case VDIR:
  110                 case VLNK:
  111                 case VREG:
  112                 case VDATABASE:
  113                         if (vp->v_mount->mnt_flag & MNT_RDONLY)
  114                                 return (EROFS);
  115                         break;
  116                 default:
  117                         break;
  118                 }
  119         }
  120 
  121         /* If immutable bit set, nobody gets to write it. */
  122         if ((mode & VWRITE) && (ino_flags & IMMUTABLE))
  123                 return (EPERM);
  124 
  125         /* Otherwise, user id 0 always gets access. */
  126         if (proc_uid == 0)
  127                 return (0);
  128 
  129         mask = 0;
  130 
  131         /* Otherwise, check the owner. */
  132         if (proc_uid == ino_uid) {
  133                 if (mode & VEXEC)
  134                         mask |= S_IXUSR;
  135                 if (mode & VREAD)
  136                         mask |= S_IRUSR;
  137                 if (mode & VWRITE)
  138                         mask |= S_IWUSR;
  139                 return ((ino_mode & mask) == mask ? 0 : EACCES);
  140         }
  141 
  142         /* 
  143          * Otherwise, check the groups. 
  144          * We must special-case the primary group to, if needed, check against
  145          * the real gid and not the effective one.
  146          */
  147         if (proc_gid == ino_gid) {
  148                 if (mode & VEXEC)
  149                         mask |= S_IXGRP;
  150                 if (mode & VREAD)
  151                         mask |= S_IRGRP;
  152                 if (mode & VWRITE)
  153                         mask |= S_IWGRP;
  154                 return ((ino_mode & mask) == mask ? 0 : EACCES);
  155         }
  156         for (i = 1, gp = &cred->cr_groups[1]; i < cred->cr_ngroups; i++, gp++)
  157                 if (ino_gid == *gp) {
  158                         if (mode & VEXEC)
  159                                 mask |= S_IXGRP;
  160                         if (mode & VREAD)
  161                                 mask |= S_IRGRP;
  162                         if (mode & VWRITE)
  163                                 mask |= S_IWGRP;
  164                         return ((ino_mode & mask) == mask ? 0 : EACCES);
  165                 }
  166 
  167         /* Otherwise, check everyone else. */
  168         if (mode & VEXEC)
  169                 mask |= S_IXOTH;
  170         if (mode & VREAD)
  171                 mask |= S_IROTH;
  172         if (mode & VWRITE)
  173                 mask |= S_IWOTH;
  174         return ((ino_mode & mask) == mask ? 0 : EACCES);
  175 }
  176 
  177 int
  178 vop_helper_setattr_flags(u_int32_t *ino_flags, u_int32_t vaflags,
  179                          uid_t uid, struct ucred *cred)
  180 {
  181         int error;
  182 
  183         /*
  184          * If uid doesn't match only a privileged user can change the flags
  185          */
  186         if (cred->cr_uid != uid &&
  187             (error = priv_check_cred(cred, PRIV_VFS_SYSFLAGS, 0))) {
  188                 return(error);
  189         }
  190         if (cred->cr_uid == 0 &&
  191             (!jailed(cred)|| jail_chflags_allowed)) {
  192                 if ((*ino_flags & (SF_NOUNLINK|SF_IMMUTABLE|SF_APPEND)) &&
  193                     securelevel > 0)
  194                         return (EPERM);
  195                 *ino_flags = vaflags;
  196         } else {
  197                 if (*ino_flags & (SF_NOUNLINK|SF_IMMUTABLE|SF_APPEND) ||
  198                     (vaflags & UF_SETTABLE) != vaflags)
  199                         return (EPERM);
  200                 *ino_flags &= SF_SETTABLE;
  201                 *ino_flags |= vaflags & UF_SETTABLE;
  202         }
  203         return(0);
  204 }
  205 
  206 /*
  207  * This helper function may be used by VFSs to implement UNIX initial
  208  * ownership semantics when creating new objects inside directories.
  209  */
  210 uid_t
  211 vop_helper_create_uid(struct mount *mp, mode_t dmode, uid_t duid,
  212                       struct ucred *cred, mode_t *modep)
  213 {
  214 #ifdef SUIDDIR
  215         if ((mp->mnt_flag & MNT_SUIDDIR) && (dmode & S_ISUID) &&
  216             duid != cred->cr_uid && duid) {
  217                 *modep &= ~07111;
  218                 return(duid);
  219         }
  220 #endif
  221         return(cred->cr_uid);
  222 }
  223 
  224 /*
  225  * This helper may be used by VFSs to implement unix chmod semantics.
  226  */
  227 int
  228 vop_helper_chmod(struct vnode *vp, mode_t new_mode, struct ucred *cred,
  229                  uid_t cur_uid, gid_t cur_gid, mode_t *cur_modep)
  230 {
  231         int error;
  232 
  233         if (cred->cr_uid != cur_uid) {
  234                 error = priv_check_cred(cred, PRIV_VFS_CHMOD, 0);
  235                 if (error)
  236                         return (error);
  237         }
  238         if (cred->cr_uid) {
  239                 if (vp->v_type != VDIR && (*cur_modep & S_ISTXT))
  240                         return (EFTYPE);
  241                 if (!groupmember(cur_gid, cred) && (*cur_modep & S_ISGID))
  242                         return (EPERM);
  243         }
  244         *cur_modep &= ~ALLPERMS;
  245         *cur_modep |= new_mode & ALLPERMS;
  246         return(0);
  247 }
  248 
  249 /*
  250  * This helper may be used by VFSs to implement unix chown semantics.
  251  */
  252 int
  253 vop_helper_chown(struct vnode *vp, uid_t new_uid, gid_t new_gid,
  254                  struct ucred *cred,
  255                  uid_t *cur_uidp, gid_t *cur_gidp, mode_t *cur_modep)
  256 {
  257         gid_t ogid;
  258         uid_t ouid;
  259         int error;
  260 
  261         if (new_uid == (uid_t)VNOVAL)
  262                 new_uid = *cur_uidp;
  263         if (new_gid == (gid_t)VNOVAL)
  264                 new_gid = *cur_gidp;
  265 
  266         /*
  267          * If we don't own the file, are trying to change the owner
  268          * of the file, or are not a member of the target group,
  269          * the caller must be privileged or the call fails.
  270          */
  271         if ((cred->cr_uid != *cur_uidp || new_uid != *cur_uidp ||
  272             (new_gid != *cur_gidp && !(cred->cr_gid == new_gid ||
  273             groupmember(new_gid, cred)))) &&
  274             (error = priv_check_cred(cred, PRIV_VFS_CHOWN, 0))) {
  275                 return (error);
  276         }
  277         ogid = *cur_gidp;
  278         ouid = *cur_uidp;
  279         /* XXX QUOTA CODE */
  280         *cur_uidp = new_uid;
  281         *cur_gidp = new_gid;
  282         /* XXX QUOTA CODE */
  283 
  284         /*
  285          * DragonFly clears both SUID and SGID if either the owner or
  286          * group is changed and root isn't doing it.  If root is doing
  287          * it we do not clear SUID/SGID.
  288          */
  289         if (cred->cr_uid != 0 && (ouid != new_uid || ogid != new_gid))
  290                 *cur_modep &= ~(S_ISUID | S_ISGID);
  291         return(0);
  292 }
  293 
  294 #ifdef LWBUF_IS_OPTIMAL
  295 
  296 /*
  297  * A VFS can call this function to try to dispose of a read request
  298  * directly from the VM system, pretty much bypassing almost all VFS
  299  * overhead except for atime updates.
  300  *
  301  * If 0 is returned some or all of the uio was handled.  The caller must
  302  * check the uio and handle the remainder.
  303  *
  304  * The caller must fail on a non-zero error.
  305  */
  306 int
  307 vop_helper_read_shortcut(struct vop_read_args *ap)
  308 {
  309         struct vnode *vp;
  310         struct uio *uio;
  311         struct lwbuf *lwb;
  312         struct lwbuf lwb_cache;
  313         vm_object_t obj;
  314         vm_page_t m;
  315         int offset;
  316         int n;
  317         int error;
  318 
  319         vp = ap->a_vp;
  320         uio = ap->a_uio;
  321 
  322         /*
  323          * We can't short-cut if there is no VM object or this is a special
  324          * UIO_NOCOPY read (typically from VOP_STRATEGY()).  We also can't
  325          * do this if we cannot extract the filesize from the vnode.
  326          */
  327         if (vm_read_shortcut_enable == 0)
  328                 return(0);
  329         if (vp->v_object == NULL || uio->uio_segflg == UIO_NOCOPY)
  330                 return(0);
  331         if (vp->v_filesize == NOOFFSET)
  332                 return(0);
  333         if (uio->uio_resid == 0)
  334                 return(0);
  335 
  336         /*
  337          * Iterate the uio on a page-by-page basis
  338          *
  339          * XXX can we leave the object held shared during the uiomove()?
  340          */
  341         ++vm_read_shortcut_count;
  342         obj = vp->v_object;
  343         vm_object_hold_shared(obj);
  344 
  345         error = 0;
  346         while (uio->uio_resid && error == 0) {
  347                 offset = (int)uio->uio_offset & PAGE_MASK;
  348                 n = PAGE_SIZE - offset;
  349                 if (n > uio->uio_resid)
  350                         n = uio->uio_resid;
  351                 if (vp->v_filesize < uio->uio_offset)
  352                         break;
  353                 if (uio->uio_offset + n > vp->v_filesize)
  354                         n = vp->v_filesize - uio->uio_offset;
  355                 if (n == 0)
  356                         break;  /* hit EOF */
  357 
  358                 m = vm_page_lookup_busy_try(obj, OFF_TO_IDX(uio->uio_offset),
  359                                             FALSE, &error);
  360                 if (error || m == NULL) {
  361                         ++vm_read_shortcut_failed;
  362                         error = 0;
  363                         break;
  364                 }
  365                 if ((m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) {
  366                         ++vm_read_shortcut_failed;
  367                         vm_page_wakeup(m);
  368                         break;
  369                 }
  370                 lwb = lwbuf_alloc(m, &lwb_cache);
  371 
  372                 /*
  373                  * Use a no-fault uiomove() to avoid deadlocking against
  374                  * our VM object (which could livelock on the same object
  375                  * due to shared-vs-exclusive), or deadlocking against
  376                  * our busied page.  Returns EFAULT on any fault which
  377                  * winds up diving a vnode.
  378                  */
  379                 error = uiomove_nofault((char *)lwbuf_kva(lwb) + offset,
  380                                         n, uio);
  381 
  382                 vm_page_flag_set(m, PG_REFERENCED);
  383                 lwbuf_free(lwb);
  384                 vm_page_wakeup(m);
  385         }
  386         vm_object_drop(obj);
  387 
  388         /*
  389          * Ignore EFAULT since we used uiomove_nofault(), causes caller
  390          * to fall-back to normal code for this case.
  391          */
  392         if (error == EFAULT)
  393                 error = 0;
  394 
  395         return (error);
  396 }
  397 
  398 #else
  399 
  400 /*
  401  * If lwbuf's aren't optimal then it's best to just use the buffer
  402  * cache.
  403  */
  404 int
  405 vop_helper_read_shortcut(struct vop_read_args *ap)
  406 {
  407         return(0);
  408 }
  409 
  410 #endif
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FreeBSD/Linux Kernel Cross Reference sys/kern/vfs_helper.c

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