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("$FreeBSD$"); 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 #ifdef KASAN 41 #error KASAN and DEBUG_REDZONE cannot be configured together 42 #endif 43 44 static SYSCTL_NODE(_vm, OID_AUTO, redzone, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 45 "RedZone data"); 46 static u_long redzone_extra_mem = 0; 47 SYSCTL_ULONG(_vm_redzone, OID_AUTO, extra_mem, CTLFLAG_RD, &redzone_extra_mem, 48 0, "Extra memory allocated by redzone"); 49 static int redzone_panic = 0; 50 SYSCTL_INT(_vm_redzone, OID_AUTO, panic, CTLFLAG_RWTUN, &redzone_panic, 0, 51 "Panic when buffer corruption is detected"); 52 53 #define REDZONE_CHSIZE (16) 54 #define REDZONE_CFSIZE (16) 55 #define REDZONE_HSIZE (sizeof(struct stack) + sizeof(u_long) + REDZONE_CHSIZE) 56 #define REDZONE_FSIZE (REDZONE_CFSIZE) 57 58 static u_long 59 redzone_roundup(u_long n) 60 { 61 62 if (n < REDZONE_HSIZE) 63 n = REDZONE_HSIZE; 64 if (n <= 128) 65 return (128); 66 else if (n <= 256) 67 return (256); 68 else if (n <= 512) 69 return (512); 70 else if (n <= 1024) 71 return (1024); 72 else if (n <= 2048) 73 return (2048); 74 return (PAGE_SIZE); 75 } 76 77 u_long 78 redzone_get_size(caddr_t naddr) 79 { 80 u_long nsize; 81 82 bcopy(naddr - REDZONE_CHSIZE - sizeof(u_long), &nsize, sizeof(nsize)); 83 return (nsize); 84 } 85 86 u_long 87 redzone_size_ntor(u_long nsize) 88 { 89 90 return (nsize + redzone_roundup(nsize) + REDZONE_FSIZE); 91 } 92 93 void * 94 redzone_addr_ntor(caddr_t naddr) 95 { 96 97 return (naddr - redzone_roundup(redzone_get_size(naddr))); 98 } 99 100 /* 101 * Set redzones and remember allocation backtrace. 102 */ 103 void * 104 redzone_setup(caddr_t raddr, u_long nsize) 105 { 106 struct stack st; 107 caddr_t haddr, faddr; 108 109 atomic_add_long(&redzone_extra_mem, redzone_size_ntor(nsize) - nsize); 110 111 haddr = raddr + redzone_roundup(nsize) - REDZONE_HSIZE; 112 faddr = haddr + REDZONE_HSIZE + nsize; 113 114 /* Redzone header. */ 115 stack_save(&st); 116 bcopy(&st, haddr, sizeof(st)); 117 haddr += sizeof(st); 118 bcopy(&nsize, haddr, sizeof(nsize)); 119 haddr += sizeof(nsize); 120 memset(haddr, 0x42, REDZONE_CHSIZE); 121 haddr += REDZONE_CHSIZE; 122 123 /* Redzone footer. */ 124 memset(faddr, 0x42, REDZONE_CFSIZE); 125 126 return (haddr); 127 } 128 129 /* 130 * Verify redzones. 131 * This function is called on free() and realloc(). 132 */ 133 void 134 redzone_check(caddr_t naddr) 135 { 136 struct stack ast, fst; 137 caddr_t haddr, faddr; 138 u_int ncorruptions; 139 u_long nsize; 140 int i; 141 142 haddr = naddr - REDZONE_HSIZE; 143 bcopy(haddr, &ast, sizeof(ast)); 144 haddr += sizeof(ast); 145 bcopy(haddr, &nsize, sizeof(nsize)); 146 haddr += sizeof(nsize); 147 148 atomic_subtract_long(&redzone_extra_mem, 149 redzone_size_ntor(nsize) - nsize); 150 151 /* Look for buffer underflow. */ 152 ncorruptions = 0; 153 for (i = 0; i < REDZONE_CHSIZE; i++, haddr++) { 154 if (*(u_char *)haddr != 0x42) 155 ncorruptions++; 156 } 157 if (ncorruptions > 0) { 158 printf("REDZONE: Buffer underflow detected. %u byte%s " 159 "corrupted before %p (%lu bytes allocated).\n", 160 ncorruptions, ncorruptions == 1 ? "" : "s", naddr, nsize); 161 printf("Allocation backtrace:\n"); 162 stack_print_ddb(&ast); 163 printf("Free backtrace:\n"); 164 stack_save(&fst); 165 stack_print_ddb(&fst); 166 if (redzone_panic) 167 panic("Stopping here."); 168 } 169 faddr = naddr + nsize; 170 /* Look for buffer overflow. */ 171 ncorruptions = 0; 172 for (i = 0; i < REDZONE_CFSIZE; i++, faddr++) { 173 if (*(u_char *)faddr != 0x42) 174 ncorruptions++; 175 } 176 if (ncorruptions > 0) { 177 printf("REDZONE: Buffer overflow detected. %u byte%s corrupted " 178 "after %p (%lu bytes allocated).\n", ncorruptions, 179 ncorruptions == 1 ? "" : "s", naddr + nsize, nsize); 180 printf("Allocation backtrace:\n"); 181 stack_print_ddb(&ast); 182 printf("Free backtrace:\n"); 183 stack_save(&fst); 184 stack_print_ddb(&fst); 185 if (redzone_panic) 186 panic("Stopping here."); 187 } 188 } 189