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malloc: Mitigate null-byte overflow attacks

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* malloc/malloc.c (_int_free): Check for corrupt prev_size vs size.
(malloc_consolidate): Likewise.
This commit is contained in:
Moritz Eckert
2018-08-16 21:08:36 -04:00
committed by DJ Delorie
parent 30a17d8c95
commit d6db68e66d
2 changed files with 9 additions and 0 deletions
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4
malloc/malloc.c
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@ -4281,6 +4281,8 @@ _int_free (mstate av, mchunkptr p, int have_lock)
prevsize = prev_size (p);
size += prevsize;
p = chunk_at_offset(p, -((long) prevsize));
if (__glibc_unlikely (chunksize(p) != prevsize))
malloc_printerr ("corrupted size vs. prev_size while consolidating");
unlink(av, p, bck, fwd);
}
@ -4442,6 +4444,8 @@ static void malloc_consolidate(mstate av)
prevsize = prev_size (p);
size += prevsize;
p = chunk_at_offset(p, -((long) prevsize));
if (__glibc_unlikely (chunksize(p) != prevsize))
malloc_printerr ("corrupted size vs. prev_size in fastbins");
unlink(av, p, bck, fwd);
}