[PATCH 5.5 103/399] bpf, sockhash: Synchronize_rcu before freeing map

Greg Kroah-Hartman
2020-02-21T08:47:55Z

From: Jakub Sitnicki <jakub@cloudflare.com>

[ Upstream commit 0b2dc83906cf1e694e48003eae5df8fa63f76fd9 ]

We need to have a synchronize_rcu before free'ing the sockhash because any
outstanding psock references will have a pointer to the map and when they
use it, this could trigger a use after free.

This is a sister fix for sockhash, following commit 2bb90e5cc90e ("bpf:
sockmap, synchronize_rcu before free'ing map") which addressed sockmap,
which comes from a manual audit.

Fixes: 604326b41a6fb ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200206111652.694507-3-jakub@cloudflare.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/core/sock_map.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 085cef5857bbf..405397801bb07 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -881,6 +881,9 @@ static void sock_hash_free(struct bpf_map *map)
/* wait for psock readers accessing its map link */
synchronize_rcu();

+ /* wait for psock readers accessing its map link */
+ synchronize_rcu();
+
bpf_map_area_free(htab->buckets);
kfree(htab);
}
--
2.20.1