lib/lzo/lzo1x_decompress_safe.c

   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         unsigned char bitstream_version;
  50
  51         op = out;
  52         ip = in;
  53
  54         if (unlikely(in_len < 3))
  55                 goto input_overrun;
  56
  57         if (likely(in_len >= 5) && likely(*ip == 17)) {
  58                 bitstream_version = ip[1];
  59                 ip += 2;
  60         } else {
  61                 bitstream_version = 0;
  62         }
  63
  64         if (*ip > 17) {
  65                 t = *ip++ - 17;
  66                 if (t < 4) {
  67                         next = t;
  68                         goto match_next;
  69                 }
  70                 goto copy_literal_run;
  71         }
  72
  73         for (;;) {
  74                 t = *ip++;
  75                 if (t < 16) {
  76                         if (likely(state == 0)) {
  77                                 if (unlikely(t == 0)) {
  78                                         size_t offset;
  79                                         const unsigned char *ip_last = ip;
  80
  81                                         while (unlikely(*ip == 0)) {
  82                                                 ip++;
  83                                                 NEED_IP(1);
  84                                         }
  85                                         offset = ip - ip_last;
  86                                         if (unlikely(offset > MAX_255_COUNT))
  87                                                 return LZO_E_ERROR;
  88
  89                                         offset = (offset << 8) - offset;
  90                                         t += offset + 15 + *ip++;
  91                                 }
  92                                 t += 3;
  93 copy_literal_run:
  94 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
  95                                 if (likely(HAVE_IP(t + 15) && HAVE_OP(t + 15))) {
  96                                         const unsigned char *ie = ip + t;
  97                                         unsigned char *oe = op + t;
  98                                         do {
  99                                                 COPY8(op, ip);
 100                                                 op += 8;
 101                                                 ip += 8;
 102                                                 COPY8(op, ip);
 103                                                 op += 8;
 104                                                 ip += 8;
 105                                         } while (ip < ie);
 106                                         ip = ie;
 107                                         op = oe;
 108                                 } else
 109 #endif
 110                                 {
 111                                         NEED_OP(t);
 112                                         NEED_IP(t + 3);
 113                                         do {
 114                                                 *op++ = *ip++;
 115                                         } while (--t > 0);
 116                                 }
 117                                 state = 4;
 118                                 continue;
 119                         } else if (state != 4) {
 120                                 next = t & 3;
 121                                 m_pos = op - 1;
 122                                 m_pos -= t >> 2;
 123                                 m_pos -= *ip++ << 2;
 124                                 TEST_LB(m_pos);
 125                                 NEED_OP(2);
 126                                 op[0] = m_pos[0];
 127                                 op[1] = m_pos[1];
 128                                 op += 2;
 129                                 goto match_next;
 130                         } else {
 131                                 next = t & 3;
 132                                 m_pos = op - (1 + M2_MAX_OFFSET);
 133                                 m_pos -= t >> 2;
 134                                 m_pos -= *ip++ << 2;
 135                                 t = 3;
 136                         }
 137                 } else if (t >= 64) {
 138                         next = t & 3;
 139                         m_pos = op - 1;
 140                         m_pos -= (t >> 2) & 7;
 141                         m_pos -= *ip++ << 3;
 142                         t = (t >> 5) - 1 + (3 - 1);
 143                 } else if (t >= 32) {
 144                         t = (t & 31) + (3 - 1);
 145                         if (unlikely(t == 2)) {
 146                                 size_t offset;
 147                                 const unsigned char *ip_last = ip;
 148
 149                                 while (unlikely(*ip == 0)) {
 150                                         ip++;
 151                                         NEED_IP(1);
 152                                 }
 153                                 offset = ip - ip_last;
 154                                 if (unlikely(offset > MAX_255_COUNT))
 155                                         return LZO_E_ERROR;
 156
 157                                 offset = (offset << 8) - offset;
 158                                 t += offset + 31 + *ip++;
 159                                 NEED_IP(2);
 160                         }
 161                         m_pos = op - 1;
 162                         next = get_unaligned_le16(ip);
 163                         ip += 2;
 164                         m_pos -= next >> 2;
 165                         next &= 3;
 166                 } else {
 167                         NEED_IP(2);
 168                         next = get_unaligned_le16(ip);
 169                         if (((next & 0xfffc) == 0xfffc) &&
 170                             ((t & 0xf8) == 0x18) &&
 171                             likely(bitstream_version)) {
 172                                 NEED_IP(3);
 173                                 t &= 7;
 174                                 t |= ip[2] << 3;
 175                                 t += MIN_ZERO_RUN_LENGTH;
 176                                 NEED_OP(t);
 177                                 memset(op, 0, t);
 178                                 op += t;
 179                                 next &= 3;
 180                                 ip += 3;
 181                                 goto match_next;
 182                         } else {
 183                                 m_pos = op;
 184                                 m_pos -= (t & 8) << 11;
 185                                 t = (t & 7) + (3 - 1);
 186                                 if (unlikely(t == 2)) {
 187                                         size_t offset;
 188                                         const unsigned char *ip_last = ip;
 189
 190                                         while (unlikely(*ip == 0)) {
 191                                                 ip++;
 192                                                 NEED_IP(1);
 193                                         }
 194                                         offset = ip - ip_last;
 195                                         if (unlikely(offset > MAX_255_COUNT))
 196                                                 return LZO_E_ERROR;
 197
 198                                         offset = (offset << 8) - offset;
 199                                         t += offset + 7 + *ip++;
 200                                         NEED_IP(2);
 201                                         next = get_unaligned_le16(ip);
 202                                 }
 203                                 ip += 2;
 204                                 m_pos -= next >> 2;
 205                                 next &= 3;
 206                                 if (m_pos == op)
 207                                         goto eof_found;
 208                                 m_pos -= 0x4000;
 209                         }
 210                 }
 211                 TEST_LB(m_pos);
 212 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
 213                 if (op - m_pos >= 8) {
 214                         unsigned char *oe = op + t;
 215                         if (likely(HAVE_OP(t + 15))) {
 216                                 do {
 217                                         COPY8(op, m_pos);
 218                                         op += 8;
 219                                         m_pos += 8;
 220                                         COPY8(op, m_pos);
 221                                         op += 8;
 222                                         m_pos += 8;
 223                                 } while (op < oe);
 224                                 op = oe;
 225                                 if (HAVE_IP(6)) {
 226                                         state = next;
 227                                         COPY4(op, ip);
 228                                         op += next;
 229                                         ip += next;
 230                                         continue;
 231                                 }
 232                         } else {
 233                                 NEED_OP(t);
 234                                 do {
 235                                         *op++ = *m_pos++;
 236                                 } while (op < oe);
 237                         }
 238                 } else
 239 #endif
 240                 {
 241                         unsigned char *oe = op + t;
 242                         NEED_OP(t);
 243                         op[0] = m_pos[0];
 244                         op[1] = m_pos[1];
 245                         op += 2;
 246                         m_pos += 2;
 247                         do {
 248                                 *op++ = *m_pos++;
 249                         } while (op < oe);
 250                 }
 251 match_next:
 252                 state = next;
 253                 t = next;
 254 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
 255                 if (likely(HAVE_IP(6) && HAVE_OP(4))) {
 256                         COPY4(op, ip);
 257                         op += t;
 258                         ip += t;
 259                 } else
 260 #endif
 261                 {
 262                         NEED_IP(t + 3);
 263                         NEED_OP(t);
 264                         while (t > 0) {
 265                                 *op++ = *ip++;
 266                                 t--;
 267                         }
 268                 }
 269         }
 270
 271 eof_found:
 272         *out_len = op - out;
 273         return (t != 3       ? LZO_E_ERROR :
 274                 ip == ip_end ? LZO_E_OK :
 275                 ip <  ip_end ? LZO_E_INPUT_NOT_CONSUMED : LZO_E_INPUT_OVERRUN);
 276
 277 input_overrun:
 278         *out_len = op - out;
 279         return LZO_E_INPUT_OVERRUN;
 280
 281 output_overrun:
 282         *out_len = op - out;
 283         return LZO_E_OUTPUT_OVERRUN;
 284
 285 lookbehind_overrun:
 286         *out_len = op - out;
 287         return LZO_E_LOOKBEHIND_OVERRUN;
 288 }
 289 #ifndef STATIC
 290 EXPORT_SYMBOL_GPL(lzo1x_decompress_safe);
 291
 292 MODULE_LICENSE("GPL");
 293 MODULE_DESCRIPTION("LZO1X Decompressor");
 294
 295 #endif