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