1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * LZO1X Decompressor from LZO
4 *
5 * Copyright (C) 1996-2012 Markus F.X.J. Oberhumer <markus@oberhumer.com>
6 *
7 * The full LZO package can be found at:
8 * http://www.oberhumer.com/opensource/lzo/
9 *
10 * Changed for Linux kernel use by:
11 * Nitin Gupta <nitingupta910@gmail.com>
12 * Richard Purdie <rpurdie@openedhand.com>
13 */
14
15 #ifndef STATIC
16 #include <linux/module.h>
17 #include <linux/kernel.h>
18 #endif
19 #include <asm/unaligned.h>
20 #include <linux/lzo.h>
21 #include "lzodefs.h"
22
23 #define HAVE_IP(x) ((size_t)(ip_end - ip) >= (size_t)(x))
24 #define HAVE_OP(x) ((size_t)(op_end - op) >= (size_t)(x))
25 #define NEED_IP(x) if (!HAVE_IP(x)) goto input_overrun
26 #define NEED_OP(x) if (!HAVE_OP(x)) goto output_overrun
27 #define TEST_LB(m_pos) if ((m_pos) < out) goto lookbehind_overrun
28
29 /* This MAX_255_COUNT is the maximum number of times we can add 255 to a base
30 * count without overflowing an integer. The multiply will overflow when
31 * multiplying 255 by more than MAXINT/255. The sum will overflow earlier
32 * depending on the base count. Since the base count is taken from a u8
33 * and a few bits, it is safe to assume that it will always be lower than
34 * or equal to 2*255, thus we can always prevent any overflow by accepting
35 * two less 255 steps. See Documentation/staging/lzo.rst for more information.
36 */
37 #define MAX_255_COUNT ((((size_t)~0) / 255) - 2)
38
39 int lzo1x_decompress_safe(const unsigned char *in, size_t in_len,
40 unsigned char *out, size_t *out_len)
41 {
42 unsigned char *op;
43 const unsigned char *ip;
44 size_t t, next;
45 size_t state = 0;
46 const unsigned char *m_pos;
47 const unsigned char * const ip_end = in + in_len;
48 unsigned char * const op_end = out + *out_len;
49
50 unsigned char bitstream_version;
51
52 op = out;
53 ip = in;
54
55 if (unlikely(in_len < 3))
56 goto input_overrun;
57
58 if (likely(in_len >= 5) && likely(*ip == 17)) {
59 bitstream_version = ip[1];
60 ip += 2;
61 } else {
62 bitstream_version = 0;
63 }
64
65 if (*ip > 17) {
66 t = *ip++ - 17;
67 if (t < 4) {
68 next = t;
69 goto match_next;
70 }
71 goto copy_literal_run;
72 }
73
74 for (;;) {
75 t = *ip++;
76 if (t < 16) {
77 if (likely(state == 0)) {
78 if (unlikely(t == 0)) {
79 size_t offset;
80 const unsigned char *ip_last = ip;
81
82 while (unlikely(*ip == 0)) {
83 ip++;
84 NEED_IP(1);
85 }
86 offset = ip - ip_last;
87 if (unlikely(offset > MAX_255_COUNT))
88 return LZO_E_ERROR;
89
90 offset = (offset << 8) - offset;
91 t += offset + 15 + *ip++;
92 }
93 t += 3;
94 copy_literal_run:
95 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
96 if (likely(HAVE_IP(t + 15) && HAVE_OP(t + 15))) {
97 const unsigned char *ie = ip + t;
98 unsigned char *oe = op + t;
99 do {
100 COPY8(op, ip);
101 op += 8;
102 ip += 8;
103 COPY8(op, ip);
104 op += 8;
105 ip += 8;
106 } while (ip < ie);
107 ip = ie;
108 op = oe;
109 } else
110 #endif
111 {
112 NEED_OP(t);
113 NEED_IP(t + 3);
114 do {
115 *op++ = *ip++;
116 } while (--t > 0);
117 }
118 state = 4;
119 continue;
120 } else if (state != 4) {
121 next = t & 3;
122 m_pos = op - 1;
123 m_pos -= t >> 2;
124 m_pos -= *ip++ << 2;
125 TEST_LB(m_pos);
126 NEED_OP(2);
127 op[0] = m_pos[0];
128 op[1] = m_pos[1];
129 op += 2;
130 goto match_next;
131 } else {
132 next = t & 3;
133 m_pos = op - (1 + M2_MAX_OFFSET);
134 m_pos -= t >> 2;
135 m_pos -= *ip++ << 2;
136 t = 3;
137 }
138 } else if (t >= 64) {
139 next = t & 3;
140 m_pos = op - 1;
141 m_pos -= (t >> 2) & 7;
142 m_pos -= *ip++ << 3;
143 t = (t >> 5) - 1 + (3 - 1);
144 } else if (t >= 32) {
145 t = (t & 31) + (3 - 1);
146 if (unlikely(t == 2)) {
147 size_t offset;
148 const unsigned char *ip_last = ip;
149
150 while (unlikely(*ip == 0)) {
151 ip++;
152 NEED_IP(1);
153 }
154 offset = ip - ip_last;
155 if (unlikely(offset > MAX_255_COUNT))
156 return LZO_E_ERROR;
157
158 offset = (offset << 8) - offset;
159 t += offset + 31 + *ip++;
160 NEED_IP(2);
161 }
162 m_pos = op - 1;
163 next = get_unaligned_le16(ip);
164 ip += 2;
165 m_pos -= next >> 2;
166 next &= 3;
167 } else {
168 NEED_IP(2);
169 next = get_unaligned_le16(ip);
170 if (((next & 0xfffc) == 0xfffc) &&
171 ((t & 0xf8) == 0x18) &&
172 likely(bitstream_version)) {
173 NEED_IP(3);
174 t &= 7;
175 t |= ip[2] << 3;
176 t += MIN_ZERO_RUN_LENGTH;
177 NEED_OP(t);
178 memset(op, 0, t);
179 op += t;
180 next &= 3;
181 ip += 3;
182 goto match_next;
183 } else {
184 m_pos = op;
185 m_pos -= (t & 8) << 11;
186 t = (t & 7) + (3 - 1);
187 if (unlikely(t == 2)) {
188 size_t offset;
189 const unsigned char *ip_last = ip;
190
191 while (unlikely(*ip == 0)) {
192 ip++;
193 NEED_IP(1);
194 }
195 offset = ip - ip_last;
196 if (unlikely(offset > MAX_255_COUNT))
197 return LZO_E_ERROR;
198
199 offset = (offset << 8) - offset;
200 t += offset + 7 + *ip++;
201 NEED_IP(2);
202 next = get_unaligned_le16(ip);
203 }
204 ip += 2;
205 m_pos -= next >> 2;
206 next &= 3;
207 if (m_pos == op)
208 goto eof_found;
209 m_pos -= 0x4000;
210 }
211 }
212 TEST_LB(m_pos);
213 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
214 if (op - m_pos >= 8) {
215 unsigned char *oe = op + t;
216 if (likely(HAVE_OP(t + 15))) {
217 do {
218 COPY8(op, m_pos);
219 op += 8;
220 m_pos += 8;
221 COPY8(op, m_pos);
222 op += 8;
223 m_pos += 8;
224 } while (op < oe);
225 op = oe;
226 if (HAVE_IP(6)) {
227 state = next;
228 COPY4(op, ip);
229 op += next;
230 ip += next;
231 continue;
232 }
233 } else {
234 NEED_OP(t);
235 do {
236 *op++ = *m_pos++;
237 } while (op < oe);
238 }
239 } else
240 #endif
241 {
242 unsigned char *oe = op + t;
243 NEED_OP(t);
244 op[0] = m_pos[0];
245 op[1] = m_pos[1];
246 op += 2;
247 m_pos += 2;
248 do {
249 *op++ = *m_pos++;
250 } while (op < oe);
251 }
252 match_next:
253 state = next;
254 t = next;
255 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
256 if (likely(HAVE_IP(6) && HAVE_OP(4))) {
257 COPY4(op, ip);
258 op += t;
259 ip += t;
260 } else
261 #endif
262 {
263 NEED_IP(t + 3);
264 NEED_OP(t);
265 while (t > 0) {
266 *op++ = *ip++;
267 t--;
268 }
269 }
270 }
271
272 eof_found:
273 *out_len = op - out;
274 return (t != 3 ? LZO_E_ERROR :
275 ip == ip_end ? LZO_E_OK :
276 ip < ip_end ? LZO_E_INPUT_NOT_CONSUMED : LZO_E_INPUT_OVERRUN);
277
278 input_overrun:
279 *out_len = op - out;
280 return LZO_E_INPUT_OVERRUN;
281
282 output_overrun:
283 *out_len = op - out;
284 return LZO_E_OUTPUT_OVERRUN;
285
286 lookbehind_overrun:
287 *out_len = op - out;
288 return LZO_E_LOOKBEHIND_OVERRUN;
289 }
290 #ifndef STATIC
291 EXPORT_SYMBOL_GPL(lzo1x_decompress_safe);
292
293 MODULE_LICENSE("GPL");
294 MODULE_DESCRIPTION("LZO1X Decompressor");
295
296 #endif
297
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