Commit 5731a879 authored by John Fastabend's avatar John Fastabend Committed by Daniel Borkmann

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: default avatarJohn Fastabend <john.fastabend@gmail.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent 51335502
...@@ -591,8 +591,15 @@ static void sock_map_free(struct bpf_map *map) ...@@ -591,8 +591,15 @@ static void sock_map_free(struct bpf_map *map)
write_lock_bh(&sock->sk_callback_lock); write_lock_bh(&sock->sk_callback_lock);
psock = smap_psock_sk(sock); psock = smap_psock_sk(sock);
smap_list_remove(psock, &stab->sock_map[i]); /* This check handles a racing sock event that can get the
smap_release_sock(psock, sock); * 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); write_unlock_bh(&sock->sk_callback_lock);
} }
rcu_read_unlock(); rcu_read_unlock();
......
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