redzone.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    3  *
    4  * Copyright (c) 2006 Pawel Jakub Dawidek <pjd@FreeBSD.org>
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 
   16  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
   17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
   20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   26  * SUCH DAMAGE.
   27  */
   28 
   29 #include <sys/cdefs.h>
   30 __FBSDID("$FreeBSD: releng/12.0/sys/vm/redzone.c 326272 2017-11-27 15:23:17Z pfg $");
   31 
   32 #include <sys/param.h>
   33 #include <sys/systm.h>
   34 #include <sys/kernel.h>
   35 #include <sys/stack.h>
   36 #include <sys/sysctl.h>
   37 
   38 #include <vm/redzone.h>
   39 
   40 
   41 static SYSCTL_NODE(_vm, OID_AUTO, redzone, CTLFLAG_RW, NULL, "RedZone data");
   42 static u_long redzone_extra_mem = 0;
   43 SYSCTL_ULONG(_vm_redzone, OID_AUTO, extra_mem, CTLFLAG_RD, &redzone_extra_mem,
   44     0, "Extra memory allocated by redzone");     
   45 static int redzone_panic = 0;
   46 SYSCTL_INT(_vm_redzone, OID_AUTO, panic, CTLFLAG_RWTUN, &redzone_panic, 0,
   47     "Panic when buffer corruption is detected");     
   48 
   49 #define REDZONE_CHSIZE  (16)
   50 #define REDZONE_CFSIZE  (16)
   51 #define REDZONE_HSIZE   (sizeof(struct stack) + sizeof(u_long) + REDZONE_CHSIZE)
   52 #define REDZONE_FSIZE   (REDZONE_CFSIZE)
   53 
   54 static u_long
   55 redzone_roundup(u_long n)
   56 {
   57 
   58         if (n < REDZONE_HSIZE)
   59                 n = REDZONE_HSIZE;
   60         if (n <= 128)
   61                 return (128);
   62         else if (n <= 256)
   63                 return (256);
   64         else if (n <= 512)
   65                 return (512);
   66         else if (n <= 1024)
   67                 return (1024);
   68         else if (n <= 2048)
   69                 return (2048);
   70         return (PAGE_SIZE);
   71 }
   72 
   73 u_long
   74 redzone_get_size(caddr_t naddr)
   75 {
   76         u_long nsize;
   77 
   78         bcopy(naddr - REDZONE_CHSIZE - sizeof(u_long), &nsize, sizeof(nsize));
   79         return (nsize);
   80 }
   81 
   82 u_long
   83 redzone_size_ntor(u_long nsize)
   84 {
   85 
   86         return (nsize + redzone_roundup(nsize) + REDZONE_FSIZE);
   87 }
   88 
   89 void *
   90 redzone_addr_ntor(caddr_t naddr)
   91 {
   92 
   93         return (naddr - redzone_roundup(redzone_get_size(naddr)));
   94 }
   95 
   96 /*
   97  * Set redzones and remember allocation backtrace.
   98  */
   99 void *
  100 redzone_setup(caddr_t raddr, u_long nsize)
  101 {
  102         struct stack st;
  103         caddr_t haddr, faddr;
  104 
  105         atomic_add_long(&redzone_extra_mem, redzone_size_ntor(nsize) - nsize);
  106 
  107         haddr = raddr + redzone_roundup(nsize) - REDZONE_HSIZE;
  108         faddr = haddr + REDZONE_HSIZE + nsize;
  109 
  110         /* Redzone header. */
  111         stack_save(&st);
  112         bcopy(&st, haddr, sizeof(st));
  113         haddr += sizeof(st);
  114         bcopy(&nsize, haddr, sizeof(nsize));
  115         haddr += sizeof(nsize);
  116         memset(haddr, 0x42, REDZONE_CHSIZE);
  117         haddr += REDZONE_CHSIZE;
  118 
  119         /* Redzone footer. */
  120         memset(faddr, 0x42, REDZONE_CFSIZE);
  121 
  122         return (haddr);
  123 }
  124 
  125 /*
  126  * Verify redzones.
  127  * This function is called on free() and realloc().
  128  */
  129 void
  130 redzone_check(caddr_t naddr)
  131 {
  132         struct stack ast, fst;
  133         caddr_t haddr, faddr;
  134         u_int ncorruptions;
  135         u_long nsize;
  136         int i;
  137 
  138         haddr = naddr - REDZONE_HSIZE;
  139         bcopy(haddr, &ast, sizeof(ast));
  140         haddr += sizeof(ast);
  141         bcopy(haddr, &nsize, sizeof(nsize));
  142         haddr += sizeof(nsize);
  143 
  144         atomic_subtract_long(&redzone_extra_mem,
  145             redzone_size_ntor(nsize) - nsize);
  146 
  147         /* Look for buffer underflow. */
  148         ncorruptions = 0;
  149         for (i = 0; i < REDZONE_CHSIZE; i++, haddr++) {
  150                 if (*(u_char *)haddr != 0x42)
  151                         ncorruptions++;
  152         }
  153         if (ncorruptions > 0) {
  154                 printf("REDZONE: Buffer underflow detected. %u byte%s "
  155                     "corrupted before %p (%lu bytes allocated).\n",
  156                     ncorruptions, ncorruptions == 1 ? "" : "s", naddr, nsize);
  157                 printf("Allocation backtrace:\n");
  158                 stack_print_ddb(&ast);
  159                 printf("Free backtrace:\n");
  160                 stack_save(&fst);
  161                 stack_print_ddb(&fst);
  162                 if (redzone_panic)
  163                         panic("Stopping here.");
  164         }
  165         faddr = naddr + nsize;
  166         /* Look for buffer overflow. */
  167         ncorruptions = 0;
  168         for (i = 0; i < REDZONE_CFSIZE; i++, faddr++) {
  169                 if (*(u_char *)faddr != 0x42)
  170                         ncorruptions++;
  171         }
  172         if (ncorruptions > 0) {
  173                 printf("REDZONE: Buffer overflow detected. %u byte%s corrupted "
  174                     "after %p (%lu bytes allocated).\n", ncorruptions,
  175                     ncorruptions == 1 ? "" : "s", naddr + nsize, nsize);
  176                 printf("Allocation backtrace:\n");
  177                 stack_print_ddb(&ast);
  178                 printf("Free backtrace:\n");
  179                 stack_save(&fst);
  180                 stack_print_ddb(&fst);
  181                 if (redzone_panic)
  182                         panic("Stopping here.");
  183         }
  184 }

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FreeBSD/Linux Kernel Cross Reference sys/vm/redzone.c

FreeBSD/Linux Kernel Cross Reference
sys/vm/redzone.c