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         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