4.19-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
commit 8873c064d1de579ea23412a6d3eee972593f142b upstream.
syzkaller was able to hit the WARN_ON(sock_owned_by_user(sk)); in tcp_close()
While a socket is being closed, it is very possible other threads find it in rtnetlink dump.
tcp_get_info() will acquire the socket lock for a short amount of time (slow = lock_sock_fast(sk)/unlock_sock_fast(sk, slow);), enough to trigger the warning.
Fixes: 67db3e4bfbc9 ("tcp: no longer hold ehash lock while calling tcp_get_info()") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- include/net/sock.h | 1 + net/core/sock.c | 2 +- net/ipv4/tcp.c | 11 +++-------- 3 files changed, 5 insertions(+), 9 deletions(-)
--- a/include/net/sock.h +++ b/include/net/sock.h @@ -1491,6 +1491,7 @@ static inline void lock_sock(struct sock lock_sock_nested(sk, 0); }
+void __release_sock(struct sock *sk); void release_sock(struct sock *sk);
/* BH context may only use the following locking interface. */ --- a/net/core/sock.c +++ b/net/core/sock.c @@ -2317,7 +2317,7 @@ static void __lock_sock(struct sock *sk) finish_wait(&sk->sk_lock.wq, &wait); }
-static void __release_sock(struct sock *sk) +void __release_sock(struct sock *sk) __releases(&sk->sk_lock.slock) __acquires(&sk->sk_lock.slock) { --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -2403,16 +2403,10 @@ adjudge_to_death: sock_hold(sk); sock_orphan(sk);
- /* It is the last release_sock in its life. It will remove backlog. */ - release_sock(sk); - - - /* Now socket is owned by kernel and we acquire BH lock - * to finish close. No need to check for user refs. - */ local_bh_disable(); bh_lock_sock(sk); - WARN_ON(sock_owned_by_user(sk)); + /* remove backlog if any, without releasing ownership. */ + __release_sock(sk);
percpu_counter_inc(sk->sk_prot->orphan_count);
@@ -2481,6 +2475,7 @@ adjudge_to_death: out: bh_unlock_sock(sk); local_bh_enable(); + release_sock(sk); sock_put(sk); } EXPORT_SYMBOL(tcp_close);