RE: [PATCH bpf 2/3] bpf, sockhash: synchronize_rcu before free'ing map
From: John Fastabend <john.fastabend@gmail.com>
Date: 2020-02-06 19:01:41
Also in:
bpf
Jakub Sitnicki wrote:
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>
---
net/core/sock_map.c | 4 ++++
1 file changed, 4 insertions(+)Nice catch thanks. As far as I know I've never seen this happen but lets get this fixed. Acked-by: John Fastabend <john.fastabend@gmail.com>
quoted hunk ↗ jump to hunk
diff --git a/net/core/sock_map.c b/net/core/sock_map.c index fd8b426dbdf3..f36e13e577a3 100644 --- a/net/core/sock_map.c +++ b/net/core/sock_map.c@@ -250,6 +250,7 @@ static void sock_map_free(struct bpf_map *map) } raw_spin_unlock_bh(&stab->lock); + /* wait for psock readers accessing its map link */ synchronize_rcu(); bpf_map_area_free(stab->sks);@@ -873,6 +874,9 @@ static void sock_hash_free(struct bpf_map *map) raw_spin_unlock_bh(&bucket->lock); } + /* wait for psock readers accessing its map link */ + synchronize_rcu(); + bpf_map_area_free(htab->buckets); kfree(htab); }-- 2.24.1