After commit 983512f3a87f ("net: Drop the lock in skb_may_tx_timestamp()") from Sebastian Andrzej Siewior, apply the same logic in nfqnl_put_sk_uidgid() to avoid touching sk->sk_callback_lock. Signed-off-by: Eric Dumazet --- net/netfilter/nfnetlink_queue.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c index f1c8049861a6b7c91c2d1fd0aa1ddb2db9a31d8f..fbe5a8d7143358906d8e77d3e7a62152fdac337b 100644 --- a/net/netfilter/nfnetlink_queue.c +++ b/net/netfilter/nfnetlink_queue.c @@ -545,14 +545,23 @@ nfqnl_put_packet_info(struct sk_buff *nlskb, struct sk_buff *packet, static int nfqnl_put_sk_uidgid(struct sk_buff *skb, struct sock *sk) { + const struct socket *sock; + const struct file *file; const struct cred *cred; if (!sk_fullsock(sk)) return 0; - read_lock_bh(&sk->sk_callback_lock); - if (sk->sk_socket && sk->sk_socket->file) { - cred = sk->sk_socket->file->f_cred; + /* The sk pointer remains valid as long as the skb is. + * The sk_socket and file pointer may become NULL + * if the socket is closed. + * Both structures (including file->cred) are RCU freed + * which means they can be accessed within a RCU read section. + */ + sock = READ_ONCE(sk->sk_socket); + file = sock ? READ_ONCE(sock->file) : NULL; + if (file) { + cred = file->f_cred; if (nla_put_be32(skb, NFQA_UID, htonl(from_kuid_munged(&init_user_ns, cred->fsuid)))) goto nla_put_failure; @@ -560,11 +569,9 @@ static int nfqnl_put_sk_uidgid(struct sk_buff *skb, struct sock *sk) htonl(from_kgid_munged(&init_user_ns, cred->fsgid)))) goto nla_put_failure; } - read_unlock_bh(&sk->sk_callback_lock); return 0; nla_put_failure: - read_unlock_bh(&sk->sk_callback_lock); return -1; } -- 2.53.0.414.gf7e9f6c205-goog