After commit 983512f3a87f ("net: Drop the lock in skb_may_tx_timestamp()") from Sebastian Andrzej Siewior, apply the same logic in nf_log_dump_sk_uid_gid() to avoid touching sk_callback_lock. Signed-off-by: Eric Dumazet --- net/netfilter/nf_log_syslog.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/net/netfilter/nf_log_syslog.c b/net/netfilter/nf_log_syslog.c index 41503847d9d7fb21824fabb1b57b45f2622b9310..dee6be17440c6c0f202fc2ba67129437879e45a6 100644 --- a/net/netfilter/nf_log_syslog.c +++ b/net/netfilter/nf_log_syslog.c @@ -165,18 +165,28 @@ static struct nf_logger nf_arp_logger __read_mostly = { static void nf_log_dump_sk_uid_gid(struct net *net, struct nf_log_buf *m, struct sock *sk) { + const struct socket *sock; + const struct file *file; + if (!sk || !sk_fullsock(sk) || !net_eq(net, sock_net(sk))) return; - read_lock_bh(&sk->sk_callback_lock); - if (sk->sk_socket && sk->sk_socket->file) { - const struct cred *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. + */ + rcu_read_lock(); + sock = READ_ONCE(sk->sk_socket); + file = sock ? READ_ONCE(sock->file) : NULL; + if (file) { + const struct cred *cred = file->f_cred; nf_log_buf_add(m, "UID=%u GID=%u ", from_kuid_munged(&init_user_ns, cred->fsuid), from_kgid_munged(&init_user_ns, cred->fsgid)); } - read_unlock_bh(&sk->sk_callback_lock); + rcu_read_unlock(); } static noinline_for_stack int -- 2.53.0.371.g1d285c8824-goog