glibc/SOURCES/glibc-rh1651283-2.patch

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2019-08-05 14:38:49 +00:00
commit 30a17d8c95fbfb15c52d1115803b63aaa73a285c
Author: Pochang Chen <johnchen902@gmail.com>
Date: Thu Aug 16 15:24:24 2018 -0400
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.
diff --git a/malloc/malloc.c b/malloc/malloc.c
index e450597e2e527fb7..d8d4581a9dcea80a 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -4084,6 +4084,9 @@ _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;