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malloc: Check the alignment of mmapped chunks before unmapping.

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* malloc/malloc.c (munmap_chunk): Verify chunk alignment.
This commit is contained in:
Istvan Kurucsai 2018-12-21 00:13:01 -05:00 committed by DJ Delorie
parent ebe544bf6e
commit c0e82f1173
2 changed files with 8 additions and 1 deletions
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ChangeLog
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@ -1,3 +1,7 @@
2018-12-21 Istvan Kurucsai <pistukem@gmail.com>
* malloc/malloc.c (munmap_chunk): Verify chunk alignment.
2018-12-20 Istvan Kurucsai <pistukem@gmail.com>
* malloc/malloc.c (mremap_chunk): Additional checks.

5
malloc/malloc.c
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@ -2889,6 +2889,7 @@ systrim (size_t pad, mstate av)
static void
munmap_chunk (mchunkptr p)
{
size_t pagesize = GLRO (dl_pagesize);
INTERNAL_SIZE_T size = chunksize (p);
assert (chunk_is_mmapped (p));
@ -2898,6 +2899,7 @@ munmap_chunk (mchunkptr p)
if (DUMPED_MAIN_ARENA_CHUNK (p))
return;
uintptr_t mem = (uintptr_t) chunk2mem (p);
uintptr_t block = (uintptr_t) p - prev_size (p);
size_t total_size = prev_size (p) + size;
/* Unfortunately we have to do the compilers job by hand here. Normally
@ -2905,7 +2907,8 @@ munmap_chunk (mchunkptr p)
page size. But gcc does not recognize the optimization possibility
(in the moment at least) so we combine the two values into one before
the bit test. */
if (__builtin_expect (((block | total_size) & (GLRO (dl_pagesize) - 1)) != 0, 0))
if (__glibc_unlikely ((block | total_size) & (pagesize - 1)) != 0
|| __glibc_unlikely (!powerof2 (mem & (pagesize - 1))))
malloc_printerr ("munmap_chunk(): invalid pointer");
atomic_decrement (&mp_.n_mmaps);