[RFC,4/7] malloc: Ensure lower bound on chunk size in __libc_realloc.
Commit Message
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(-)
@@ -2989,8 +2989,9 @@ __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 (check_action, "realloc(): invalid pointer", oldmem,