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

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2006 Pawel Jakub Dawidek <pjd@FreeBSD.org>
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 
     * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/kernel.h>
    #include <sys/stack.h>
    #include <sys/sysctl.h>
    
    #include <vm/redzone.h>
    
    #ifdef KASAN
    #error KASAN and DEBUG_REDZONE cannot be configured together
    #endif
    
    static SYSCTL_NODE(_vm, OID_AUTO, redzone, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
        "RedZone data");
    static u_long redzone_extra_mem = 0;
    SYSCTL_ULONG(_vm_redzone, OID_AUTO, extra_mem, CTLFLAG_RD, &redzone_extra_mem,
        0, "Extra memory allocated by redzone");     
    static int redzone_panic = 0;
    SYSCTL_INT(_vm_redzone, OID_AUTO, panic, CTLFLAG_RWTUN, &redzone_panic, 0,
        "Panic when buffer corruption is detected");     
    
    #define REDZONE_CHSIZE  (16)
    #define REDZONE_CFSIZE  (16)
    #define REDZONE_HSIZE   (sizeof(struct stack) + sizeof(u_long) + REDZONE_CHSIZE)
    #define REDZONE_FSIZE   (REDZONE_CFSIZE)
    
    static u_long
    redzone_roundup(u_long n)
    {
    
            if (n < REDZONE_HSIZE)
                    n = REDZONE_HSIZE;
            if (n <= 128)
                    return (128);
            else if (n <= 256)
                    return (256);
            else if (n <= 512)
                    return (512);
            else if (n <= 1024)
                    return (1024);
            else if (n <= 2048)
                    return (2048);
            return (PAGE_SIZE);
    }
    
    u_long
    redzone_get_size(caddr_t naddr)
    {
            u_long nsize;
    
            bcopy(naddr - REDZONE_CHSIZE - sizeof(u_long), &nsize, sizeof(nsize));
            return (nsize);
    }
    
    u_long
    redzone_size_ntor(u_long nsize)
    {
    
            return (nsize + redzone_roundup(nsize) + REDZONE_FSIZE);
    }
    
    void *
    redzone_addr_ntor(caddr_t naddr)
    {
    
            return (naddr - redzone_roundup(redzone_get_size(naddr)));
    }
    
   /*
    * Set redzones and remember allocation backtrace.
    */
   void *
   redzone_setup(caddr_t raddr, u_long nsize)
   {
           struct stack st;
           caddr_t haddr, faddr;
   
           atomic_add_long(&redzone_extra_mem, redzone_size_ntor(nsize) - nsize);
   
           haddr = raddr + redzone_roundup(nsize) - REDZONE_HSIZE;
           faddr = haddr + REDZONE_HSIZE + nsize;
   
           /* Redzone header. */
           stack_save(&st);
           bcopy(&st, haddr, sizeof(st));
           haddr += sizeof(st);
           bcopy(&nsize, haddr, sizeof(nsize));
           haddr += sizeof(nsize);
           memset(haddr, 0x42, REDZONE_CHSIZE);
           haddr += REDZONE_CHSIZE;
   
           /* Redzone footer. */
           memset(faddr, 0x42, REDZONE_CFSIZE);
   
           return (haddr);
   }
   
   /*
    * Verify redzones.
    * This function is called on free() and realloc().
    */
   void
   redzone_check(caddr_t naddr)
   {
           struct stack ast, fst;
           caddr_t haddr, faddr;
           u_int ncorruptions;
           u_long nsize;
           int i;
   
           haddr = naddr - REDZONE_HSIZE;
           bcopy(haddr, &ast, sizeof(ast));
           haddr += sizeof(ast);
           bcopy(haddr, &nsize, sizeof(nsize));
           haddr += sizeof(nsize);
   
           atomic_subtract_long(&redzone_extra_mem,
               redzone_size_ntor(nsize) - nsize);
   
           /* Look for buffer underflow. */
           ncorruptions = 0;
           for (i = 0; i < REDZONE_CHSIZE; i++, haddr++) {
                   if (*(u_char *)haddr != 0x42)
                           ncorruptions++;
           }
           if (ncorruptions > 0) {
                   printf("REDZONE: Buffer underflow detected. %u byte%s "
                       "corrupted before %p (%lu bytes allocated).\n",
                       ncorruptions, ncorruptions == 1 ? "" : "s", naddr, nsize);
                   printf("Allocation backtrace:\n");
                   stack_print_ddb(&ast);
                   printf("Free backtrace:\n");
                   stack_save(&fst);
                   stack_print_ddb(&fst);
                   if (redzone_panic)
                           panic("Stopping here.");
           }
           faddr = naddr + nsize;
           /* Look for buffer overflow. */
           ncorruptions = 0;
           for (i = 0; i < REDZONE_CFSIZE; i++, faddr++) {
                   if (*(u_char *)faddr != 0x42)
                           ncorruptions++;
           }
           if (ncorruptions > 0) {
                   printf("REDZONE: Buffer overflow detected. %u byte%s corrupted "
                       "after %p (%lu bytes allocated).\n", ncorruptions,
                       ncorruptions == 1 ? "" : "s", naddr + nsize, nsize);
                   printf("Allocation backtrace:\n");
                   stack_print_ddb(&ast);
                   printf("Free backtrace:\n");
                   stack_save(&fst);
                   stack_print_ddb(&fst);
                   if (redzone_panic)
                           panic("Stopping here.");
           }
   }

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