1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
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/param.h>
30 #include <sys/systm.h>
31 #include <sys/kernel.h>
32 #include <sys/stack.h>
33 #include <sys/sysctl.h>
34
35 #include <vm/redzone.h>
36
37 #ifdef KASAN
38 #error KASAN and DEBUG_REDZONE cannot be configured together
39 #endif
40
41 static SYSCTL_NODE(_vm, OID_AUTO, redzone, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
42 "RedZone data");
43 static u_long redzone_extra_mem = 0;
44 SYSCTL_ULONG(_vm_redzone, OID_AUTO, extra_mem, CTLFLAG_RD, &redzone_extra_mem,
45 0, "Extra memory allocated by redzone");
46 static int redzone_panic = 0;
47 SYSCTL_INT(_vm_redzone, OID_AUTO, panic, CTLFLAG_RWTUN, &redzone_panic, 0,
48 "Panic when buffer corruption is detected");
49
50 #define REDZONE_CHSIZE (16)
51 #define REDZONE_CFSIZE (16)
52 #define REDZONE_HSIZE (sizeof(struct stack) + sizeof(u_long) + REDZONE_CHSIZE)
53 #define REDZONE_FSIZE (REDZONE_CFSIZE)
54
55 static u_long
redzone_roundup(u_long n)56 redzone_roundup(u_long n)
57 {
58
59 if (n < REDZONE_HSIZE)
60 n = REDZONE_HSIZE;
61 if (n <= 128)
62 return (128);
63 else if (n <= 256)
64 return (256);
65 else if (n <= 512)
66 return (512);
67 else if (n <= 1024)
68 return (1024);
69 else if (n <= 2048)
70 return (2048);
71 return (PAGE_SIZE);
72 }
73
74 u_long
redzone_get_size(caddr_t naddr)75 redzone_get_size(caddr_t naddr)
76 {
77 u_long nsize;
78
79 bcopy(naddr - REDZONE_CHSIZE - sizeof(u_long), &nsize, sizeof(nsize));
80 return (nsize);
81 }
82
83 u_long
redzone_size_ntor(u_long nsize)84 redzone_size_ntor(u_long nsize)
85 {
86
87 return (nsize + redzone_roundup(nsize) + REDZONE_FSIZE);
88 }
89
90 void *
redzone_addr_ntor(caddr_t naddr)91 redzone_addr_ntor(caddr_t naddr)
92 {
93
94 return (naddr - redzone_roundup(redzone_get_size(naddr)));
95 }
96
97 /*
98 * Set redzones and remember allocation backtrace.
99 */
100 void *
redzone_setup(caddr_t raddr,u_long nsize)101 redzone_setup(caddr_t raddr, u_long nsize)
102 {
103 struct stack st;
104 caddr_t haddr, faddr;
105
106 atomic_add_long(&redzone_extra_mem, redzone_size_ntor(nsize) - nsize);
107
108 haddr = raddr + redzone_roundup(nsize) - REDZONE_HSIZE;
109 faddr = haddr + REDZONE_HSIZE + nsize;
110
111 /* Redzone header. */
112 stack_save(&st);
113 bcopy(&st, haddr, sizeof(st));
114 haddr += sizeof(st);
115 bcopy(&nsize, haddr, sizeof(nsize));
116 haddr += sizeof(nsize);
117 memset(haddr, 0x42, REDZONE_CHSIZE);
118 haddr += REDZONE_CHSIZE;
119
120 /* Redzone footer. */
121 memset(faddr, 0x42, REDZONE_CFSIZE);
122
123 return (haddr);
124 }
125
126 /*
127 * Verify redzones.
128 * This function is called on free() and realloc().
129 */
130 void
redzone_check(caddr_t naddr)131 redzone_check(caddr_t naddr)
132 {
133 struct stack ast, fst;
134 caddr_t haddr, faddr;
135 u_int ncorruptions;
136 u_long nsize;
137 int i;
138
139 haddr = naddr - REDZONE_HSIZE;
140 bcopy(haddr, &ast, sizeof(ast));
141 haddr += sizeof(ast);
142 bcopy(haddr, &nsize, sizeof(nsize));
143 haddr += sizeof(nsize);
144
145 atomic_subtract_long(&redzone_extra_mem,
146 redzone_size_ntor(nsize) - nsize);
147
148 /* Look for buffer underflow. */
149 ncorruptions = 0;
150 for (i = 0; i < REDZONE_CHSIZE; i++, haddr++) {
151 if (*(u_char *)haddr != 0x42)
152 ncorruptions++;
153 }
154 if (ncorruptions > 0) {
155 printf("REDZONE: Buffer underflow detected. %u byte%s "
156 "corrupted before %p (%lu bytes allocated).\n",
157 ncorruptions, ncorruptions == 1 ? "" : "s", naddr, nsize);
158 printf("Allocation backtrace:\n");
159 stack_print_ddb(&ast);
160 printf("Free backtrace:\n");
161 stack_save(&fst);
162 stack_print_ddb(&fst);
163 if (redzone_panic)
164 panic("Stopping here.");
165 }
166 faddr = naddr + nsize;
167 /* Look for buffer overflow. */
168 ncorruptions = 0;
169 for (i = 0; i < REDZONE_CFSIZE; i++, faddr++) {
170 if (*(u_char *)faddr != 0x42)
171 ncorruptions++;
172 }
173 if (ncorruptions > 0) {
174 printf("REDZONE: Buffer overflow detected. %u byte%s corrupted "
175 "after %p (%lu bytes allocated).\n", ncorruptions,
176 ncorruptions == 1 ? "" : "s", naddr + nsize, nsize);
177 printf("Allocation backtrace:\n");
178 stack_print_ddb(&ast);
179 printf("Free backtrace:\n");
180 stack_save(&fst);
181 stack_print_ddb(&fst);
182 if (redzone_panic)
183 panic("Stopping here.");
184 }
185 }
186