From 5b06f538c5aee0389ed034f60d90a8884d6d54de Mon Sep 17 00:00:00 2001 From: Adam Maris Date: Thu, 14 Mar 2019 16:51:16 -0400 Subject: [PATCH] malloc: Check for large bin list corruption when inserting unsorted chunk Fixes bug 24216. This patch adds security checks for bk and bk_nextsize pointers of chunks in large bin when inserting chunk from unsorted bin. It was possible to write the pointer to victim (newly inserted chunk) to arbitrary memory locations if bk or bk_nextsize pointers of the next large bin chunk got corrupted. --- malloc/malloc.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/malloc/malloc.c b/malloc/malloc.c index 6e766d11bc..801ba1f499 100644 --- a/malloc/malloc.c +++ b/malloc/malloc.c @@ -3876,10 +3876,14 @@ _int_malloc (mstate av, size_t bytes) { victim->fd_nextsize = fwd; victim->bk_nextsize = fwd->bk_nextsize; + if (__glibc_unlikely (fwd->bk_nextsize->fd_nextsize != fwd)) + malloc_printerr ("malloc(): largebin double linked list corrupted (nextsize)"); fwd->bk_nextsize = victim; victim->bk_nextsize->fd_nextsize = victim; } bck = fwd->bk; + if (bck->fd != fwd) + malloc_printerr ("malloc(): largebin double linked list corrupted (bk)"); } } else