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
Reported-by: syzbot
---
include/net/sock.h | 1 +
net/core/sock.c| 2 +-
net/ipv4/tcp.c | 11 +++
3 files changed, 5 insertions(+), 9 deletions(-)
diff --git a/include/net/sock.h b/include/net/sock.h
index
38cae35f6e16056c862b29dee8ceb46fe16fff7b..751549ac0a849144ab0382203ee5c877374523e2
100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1492,6 +1492,7 @@ static inline void lock_sock(struct sock *sk)
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. */
diff --git a/net/core/sock.c b/net/core/sock.c
index
8537b6ca72c5013a75c70978c079646f6278aabf..7e8796a6a0892efbb7dfce67d12b8062b2d5daa9
100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2317,7 +2317,7 @@ static void __lock_sock(struct sock *sk)
finish_wait(>sk_lock.wq, );
}
-static void __release_sock(struct sock *sk)
+void __release_sock(struct sock *sk)
__releases(>sk_lock.slock)
__acquires(>sk_lock.slock)
{
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index
2827fa5643bde84633b174914bbb13a8273e9d32..43ef83b2330e6238a55c9843580a585d87708e0c
100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2416,16 +2416,10 @@ void tcp_close(struct sock *sk, long timeout)
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);
@@ -2494,6 +2488,7 @@ void tcp_close(struct sock *sk, long timeout)
out:
bh_unlock_sock(sk);
local_bh_enable();
+ release_sock(sk);
sock_put(sk);
}
EXPORT_SYMBOL(tcp_close);
--
2.19.0.605.g01d371f741-goog
