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
41static SYSCTL_NODE(_vm, OID_AUTO, redzone, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
42    "RedZone data");
43static u_long redzone_extra_mem = 0;
44SYSCTL_ULONG(_vm_redzone, OID_AUTO, extra_mem, CTLFLAG_RD, &redzone_extra_mem,
45    0, "Extra memory allocated by redzone");
46static int redzone_panic = 0;
47SYSCTL_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
55static u_long
56redzone_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
74u_long
75redzone_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
83u_long
84redzone_size_ntor(u_long nsize)
85{
86
87	return (nsize + redzone_roundup(nsize) + REDZONE_FSIZE);
88}
89
90void *
91redzone_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 */
100void *
101redzone_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 */
130void
131redzone_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