From 7e40c3f804b5d5dbbc0519565b16101ab22fb899 Mon Sep 17 00:00:00 2001 From: Moritz Eckert Date: Thu, 16 Aug 2018 21:08:36 -0400 Subject: [PATCH 3/8] malloc: Mitigate null-byte overflow attacks * malloc/malloc.c (_int_free): Check for corrupt prev_size vs size. (malloc_consolidate): Likewise. (cherry picked from commit d6db68e66dff25d12c3bc5641b60cbd7fb6ab44f) --- ChangeLog | 5 +++++ malloc/malloc.c | 4 ++++ 2 files changed, 9 insertions(+) diff --git a/ChangeLog b/ChangeLog index 44795b2e61..e81991066e 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,8 @@ +2018-08-16 DJ Delorie + + * malloc/malloc.c (_int_free): Check for corrupt prev_size vs size. + (malloc_consolidate): Likewise. + 2018-08-16 Pochang Chen * malloc/malloc.c (_int_malloc.c): Verify size of top chunk. diff --git a/malloc/malloc.c b/malloc/malloc.c index 9431108626..7c8bf8413c 100644 --- a/malloc/malloc.c +++ b/malloc/malloc.c @@ -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); } -- 2.17.2