Message ID | 1510068430-27816-5-git-send-email-pistukem@gmail.com |
---|---|
State | New |
Headers | show |
Series | Additional integrity checks for the malloc | expand |
On 11/07/2017 04:27 PM, Istvan Kurucsai wrote: > Under some circumstances, a chunk size of SIZE_SZ could lead to an underflow > when calculating the length argument of memcpy. > > * malloc/malloc.c (__libc_realloc): Check chunk size. > --- > malloc/malloc.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/malloc/malloc.c b/malloc/malloc.c > index 51d703c..8e48952 100644 > --- a/malloc/malloc.c > +++ b/malloc/malloc.c > @@ -3154,8 +3154,9 @@ __libc_realloc (void *oldmem, size_t bytes) > accident or by "design" from some intruder. We need to bypass > this check for dumped fake mmap chunks from the old main arena > because the new malloc may provide additional alignment. */ > - if ((__builtin_expect ((uintptr_t) oldp > (uintptr_t) -oldsize, 0) > - || __builtin_expect (misaligned_chunk (oldp), 0)) > + if ((__glibc_unlikely ((uintptr_t) oldp > (uintptr_t) -oldsize) > + || __glibc_unlikely (misaligned_chunk (oldp)) > + || __glibc_unlikely (oldsize <= 2 * SIZE_SZ)) > && !DUMPED_MAIN_ARENA_CHUNK (oldp)) > malloc_printerr ("realloc(): invalid pointer"); DJ, can you benchmark this change? If it turns out this is visible in profiles, we may have to move this check closer to the actual memcpy. Thanks, Florian
diff --git a/malloc/malloc.c b/malloc/malloc.c index 51d703c..8e48952 100644 --- a/malloc/malloc.c +++ b/malloc/malloc.c @@ -3154,8 +3154,9 @@ __libc_realloc (void *oldmem, size_t bytes) accident or by "design" from some intruder. We need to bypass this check for dumped fake mmap chunks from the old main arena because the new malloc may provide additional alignment. */ - if ((__builtin_expect ((uintptr_t) oldp > (uintptr_t) -oldsize, 0) - || __builtin_expect (misaligned_chunk (oldp), 0)) + if ((__glibc_unlikely ((uintptr_t) oldp > (uintptr_t) -oldsize) + || __glibc_unlikely (misaligned_chunk (oldp)) + || __glibc_unlikely (oldsize <= 2 * SIZE_SZ)) && !DUMPED_MAIN_ARENA_CHUNK (oldp)) malloc_printerr ("realloc(): invalid pointer");