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Linux/lib/lzo/lzo1x_decompress_safe.c

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  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 
 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 

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