path: root/malloc
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authorPochang Chen <johnchen902@gmail.com>2018-08-16 15:24:24 -0400
committerDJ Delorie <dj@delorie.com>2018-08-16 15:24:24 -0400
commit30a17d8c95fbfb15c52d1115803b63aaa73a285c (patch)
tree9cc656df2264773490117fda7628fd9abf4dd943 /malloc
parent34f86d61687457aa57d40cf3c230ca8404d40e45 (diff)
malloc: Verify size of top chunk.
The House of Force is a well-known technique to exploit heap overflow. In essence, this exploit takes three steps: 1. Overwrite the size of top chunk with very large value (e.g. -1). 2. Request x bytes from top chunk. As the size of top chunk is corrupted, x can be arbitrarily large and top chunk will still be offset by x. 3. The next allocation from top chunk will thus be controllable. If we verify the size of top chunk at step 2, we can stop such attack.
Diffstat (limited to 'malloc')
1 files changed, 3 insertions, 0 deletions
diff --git a/malloc/malloc.c b/malloc/malloc.c
index e247c77b7d4..9431108626c 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -4076,6 +4076,9 @@ _int_malloc (mstate av, size_t bytes)
victim = av->top;
size = chunksize (victim);
+ if (__glibc_unlikely (size > av->system_mem))
+ malloc_printerr ("malloc(): corrupted top size");
if ((unsigned long) (size) >= (unsigned long) (nb + MINSIZE))
remainder_size = size - nb;