diff options
Diffstat (limited to 'malloc')
| -rw-r--r-- | malloc/hooks.c | 79 |
1 files changed, 44 insertions, 35 deletions
diff --git a/malloc/hooks.c b/malloc/hooks.c index 00ee6bec8c..996111a7e3 100644 --- a/malloc/hooks.c +++ b/malloc/hooks.c @@ -90,31 +90,35 @@ __malloc_check_init (void) #define MAGICBYTE(p) ((((size_t) p >> 3) ^ ((size_t) p >> 11)) & 0xFF) -/* Visualize the chunk as being partitioned into blocks of 256 bytes from the - highest address of the chunk, downwards. The beginning of each block tells - us the size of the previous block, up to the actual size of the requested - memory. Our magic byte is right at the end of the requested size, so we - must reach it with this iteration, otherwise we have witnessed a memory - corruption. */ +/* Visualize the chunk as being partitioned into blocks of 255 bytes from the + highest address of the chunk, downwards. The end of each block tells us + the size of that block, up to the actual size of the requested memory. + The last block has a length of zero and is followed by the magic byte. + Our magic byte is right at the end of the requested size. If we don't + reach it with this iteration we have witnessed a memory corruption. */ static size_t malloc_check_get_size (mchunkptr p) { - size_t size; + size_t total_sz, size; unsigned char c; unsigned char magic = MAGICBYTE (p); assert (using_malloc_checking == 1); - for (size = chunksize (p) - 1 + (chunk_is_mmapped (p) ? 0 : SIZE_SZ); - (c = ((unsigned char *) p)[size]) != magic; + /* Validate the length-byte chain. */ + total_sz = chunksize (p) + (chunk_is_mmapped (p) ? 0 : SIZE_SZ); + for (size = total_sz - 1; + (c = ((unsigned char *) p)[size]) != 0; size -= c) { - if (c <= 0 || size < (c + 2 * SIZE_SZ)) - { - malloc_printerr (check_action, "malloc_check_get_size: memory corruption", - chunk2mem (p)); - return 0; - } + if (size <= c + 2 * SIZE_SZ) + break; + } + if (c != 0 || ((unsigned char *) p)[--size] != magic) + { + malloc_printerr (check_action, "malloc_check_get_size: memory corruption", + chunk2mem (p)); + return 0; } /* chunk2mem size. */ @@ -130,22 +134,24 @@ mem2mem_check (void *ptr, size_t sz) { mchunkptr p; unsigned char *m_ptr = ptr; - size_t i; + size_t user_sz, block_sz, i; if (!ptr) return ptr; p = mem2chunk (ptr); - for (i = chunksize (p) - (chunk_is_mmapped (p) ? 2 * SIZE_SZ + 1 : SIZE_SZ + 1); - i > sz; - i -= 0xFF) + user_sz = chunksize (p) + (chunk_is_mmapped (p) ? 0 : SIZE_SZ); + user_sz -= 2 * SIZE_SZ; + for (i = user_sz - 1; i > sz; i -= block_sz) { - if (i - sz < 0x100) - { - m_ptr[i] = (unsigned char) (i - sz); - break; - } - m_ptr[i] = 0xFF; + block_sz = i - (sz + 1); + if (block_sz > 0xff) + block_sz = 0xff; + + m_ptr[i] = (unsigned char) block_sz; + + if (block_sz == 0) + break; } m_ptr[sz] = MAGICBYTE (p); return (void *) m_ptr; @@ -166,11 +172,12 @@ mem2chunk_check (void *mem, unsigned char **magic_p) return NULL; p = mem2chunk (mem); + sz = chunksize (p); + magic = MAGICBYTE (p); if (!chunk_is_mmapped (p)) { /* Must be a chunk in conventional heap memory. */ int contig = contiguous (&main_arena); - sz = chunksize (p); if ((contig && ((char *) p < mp_.sbrk_base || ((char *) p + sz) >= (mp_.sbrk_base + main_arena.system_mem))) || @@ -180,12 +187,13 @@ mem2chunk_check (void *mem, unsigned char **magic_p) next_chunk (prev_chunk (p)) != p))) return NULL; - magic = MAGICBYTE (p); - for (sz += SIZE_SZ - 1; (c = ((unsigned char *) p)[sz]) != magic; sz -= c) + for (sz += SIZE_SZ - 1; (c = ((unsigned char *) p)[sz]) != 0; sz -= c) { - if (c <= 0 || sz < (c + 2 * SIZE_SZ)) - return NULL; + if (sz <= c + 2 * SIZE_SZ) + break; } + if (c != 0 || ((unsigned char *) p)[--sz] != magic) + return NULL; } else { @@ -201,15 +209,16 @@ mem2chunk_check (void *mem, unsigned char **magic_p) offset < 0x2000) || !chunk_is_mmapped (p) || (p->size & PREV_INUSE) || ((((unsigned long) p - p->prev_size) & page_mask) != 0) || - ((sz = chunksize (p)), ((p->prev_size + sz) & page_mask) != 0)) + ((p->prev_size + sz) & page_mask) != 0) return NULL; - magic = MAGICBYTE (p); - for (sz -= 1; (c = ((unsigned char *) p)[sz]) != magic; sz -= c) + for (sz -= 1; (c = ((unsigned char *) p)[sz]) != 0; sz -= c) { - if (c <= 0 || sz < (c + 2 * SIZE_SZ)) - return NULL; + if (sz <= c + 2 * SIZE_SZ) + break; } + if (c != 0 || ((unsigned char *) p)[--sz] != magic) + return NULL; } ((unsigned char *) p)[sz] ^= 0xFF; if (magic_p) |