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authorJohn Fastabend <john.fastabend@gmail.com>2018-01-04 20:02:09 -0800
committerDaniel Borkmann <daniel@iogearbox.net>2018-01-07 00:01:46 +0100
commit5731a879d03bdaa00265f8ebc32dfd0e65d25276 (patch)
tree3a9d68d5c946353b0f0583e3440655e555826d60 /kernel
parent5133550296d43236439494aa955bfb765a89f615 (diff)
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bpf: sockmap missing NULL psock check
Add psock NULL check to handle a racing sock event that can get the sk_callback_lock before this case but after xchg happens causing the refcnt to hit zero and sock user data (psock) to be null and queued for garbage collection. Also add a comment in the code because this is a bit subtle and not obvious in my opinion. Signed-off-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/sockmap.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index 5ee2e41893d9..1712d319c2d8 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -591,8 +591,15 @@ static void sock_map_free(struct bpf_map *map)
write_lock_bh(&sock->sk_callback_lock);
psock = smap_psock_sk(sock);
- smap_list_remove(psock, &stab->sock_map[i]);
- smap_release_sock(psock, sock);
+ /* This check handles a racing sock event that can get the
+ * sk_callback_lock before this case but after xchg happens
+ * causing the refcnt to hit zero and sock user data (psock)
+ * to be null and queued for garbage collection.
+ */
+ if (likely(psock)) {
+ smap_list_remove(psock, &stab->sock_map[i]);
+ smap_release_sock(psock, sock);
+ }
write_unlock_bh(&sock->sk_callback_lock);
}
rcu_read_unlock();