xref: /freebsd/sys/vm/redzone.c (revision 39beb93c3f8bdbf72a61fda42300b5ebed7390c8)
1 /*-
2  * Copyright (c) 2006 Pawel Jakub Dawidek <pjd@FreeBSD.org>
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24  * SUCH DAMAGE.
25  */
26 
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD$");
29 
30 #include <sys/param.h>
31 #include <sys/systm.h>
32 #include <sys/kernel.h>
33 #include <sys/stack.h>
34 #include <sys/sysctl.h>
35 
36 #include <vm/redzone.h>
37 
38 
39 SYSCTL_NODE(_vm, OID_AUTO, redzone, CTLFLAG_RW, NULL, "RedZone data");
40 static u_long redzone_extra_mem = 0;
41 SYSCTL_ULONG(_vm_redzone, OID_AUTO, extra_mem, CTLFLAG_RD, &redzone_extra_mem,
42     0, "Extra memory allocated by redzone");
43 static int redzone_panic = 0;
44 TUNABLE_INT("vm.redzone.panic", &redzone_panic);
45 SYSCTL_INT(_vm_redzone, OID_AUTO, panic, CTLFLAG_RW, &redzone_panic, 0,
46     "Panic when buffer corruption is detected");
47 
48 #define	REDZONE_CHSIZE	(16)
49 #define	REDZONE_CFSIZE	(16)
50 #define	REDZONE_HSIZE	(sizeof(struct stack) + sizeof(u_long) + REDZONE_CHSIZE)
51 #define	REDZONE_FSIZE	(REDZONE_CFSIZE)
52 
53 static u_long
54 redzone_roundup(u_long n)
55 {
56 
57 	if (n < REDZONE_HSIZE)
58 		n = REDZONE_HSIZE;
59 	if (n <= 128)
60 		return (128);
61 	else if (n <= 256)
62 		return (256);
63 	else if (n <= 512)
64 		return (512);
65 	else if (n <= 1024)
66 		return (1024);
67 	else if (n <= 2048)
68 		return (2048);
69 	return (PAGE_SIZE);
70 }
71 
72 u_long
73 redzone_get_size(caddr_t naddr)
74 {
75 	u_long nsize;
76 
77 	bcopy(naddr - REDZONE_CHSIZE - sizeof(u_long), &nsize, sizeof(nsize));
78 	return (nsize);
79 }
80 
81 u_long
82 redzone_size_ntor(u_long nsize)
83 {
84 
85 	return (nsize + redzone_roundup(nsize) + REDZONE_FSIZE);
86 }
87 
88 void *
89 redzone_addr_ntor(caddr_t naddr)
90 {
91 
92 	return (naddr - redzone_roundup(redzone_get_size(naddr)));
93 }
94 
95 /*
96  * Set redzones and remember allocation backtrace.
97  */
98 void *
99 redzone_setup(caddr_t raddr, u_long nsize)
100 {
101 	struct stack st;
102 	caddr_t haddr, faddr;
103 
104 	atomic_add_long(&redzone_extra_mem, redzone_size_ntor(nsize) - nsize);
105 
106 	haddr = raddr + redzone_roundup(nsize) - REDZONE_HSIZE;
107 	faddr = haddr + REDZONE_HSIZE + nsize;
108 
109 	/* Redzone header. */
110 	stack_save(&st);
111 	bcopy(&st, haddr, sizeof(st));
112 	haddr += sizeof(st);
113 	bcopy(&nsize, haddr, sizeof(nsize));
114 	haddr += sizeof(nsize);
115 	memset(haddr, 0x42, REDZONE_CHSIZE);
116 	haddr += REDZONE_CHSIZE;
117 
118 	/* Redzone footer. */
119 	memset(faddr, 0x42, REDZONE_CFSIZE);
120 
121 	return (haddr);
122 }
123 
124 /*
125  * Verify redzones.
126  * This function is called on free() and realloc().
127  */
128 void
129 redzone_check(caddr_t naddr)
130 {
131 	struct stack ast, fst;
132 	caddr_t haddr, faddr;
133 	u_int ncorruptions;
134 	u_long nsize;
135 	int i;
136 
137 	haddr = naddr - REDZONE_HSIZE;
138 	bcopy(haddr, &ast, sizeof(ast));
139 	haddr += sizeof(ast);
140 	bcopy(haddr, &nsize, sizeof(nsize));
141 	haddr += sizeof(nsize);
142 
143 	atomic_subtract_long(&redzone_extra_mem,
144 	    redzone_size_ntor(nsize) - nsize);
145 
146 	/* Look for buffer underflow. */
147 	ncorruptions = 0;
148 	for (i = 0; i < REDZONE_CHSIZE; i++, haddr++) {
149 		if (*(u_char *)haddr != 0x42)
150 			ncorruptions++;
151 	}
152 	if (ncorruptions > 0) {
153 		printf("REDZONE: Buffer underflow detected. %u byte%s "
154 		    "corrupted before %p (%lu bytes allocated).\n",
155 		    ncorruptions, ncorruptions == 1 ? "" : "s", naddr, nsize);
156 		printf("Allocation backtrace:\n");
157 		stack_print_ddb(&ast);
158 		printf("Free backtrace:\n");
159 		stack_save(&fst);
160 		stack_print_ddb(&fst);
161 		if (redzone_panic)
162 			panic("Stopping here.");
163 	}
164 	faddr = naddr + nsize;
165 	/* Look for buffer overflow. */
166 	ncorruptions = 0;
167 	for (i = 0; i < REDZONE_CFSIZE; i++, faddr++) {
168 		if (*(u_char *)faddr != 0x42)
169 			ncorruptions++;
170 	}
171 	if (ncorruptions > 0) {
172 		printf("REDZONE: Buffer overflow detected. %u byte%s corrupted "
173 		    "after %p (%lu bytes allocated).\n", ncorruptions,
174 		    ncorruptions == 1 ? "" : "s", naddr + nsize, nsize);
175 		printf("Allocation backtrace:\n");
176 		stack_print_ddb(&ast);
177 		printf("Free backtrace:\n");
178 		stack_save(&fst);
179 		stack_print_ddb(&fst);
180 		if (redzone_panic)
181 			panic("Stopping here.");
182 	}
183 }
184