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tcp: do not release socket ownership in tcp_close() 

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: 67db3e4bfb ("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>
This commit is contained in:
Eric Dumazet 2018-10-01 23:24:26 -07:00 committed by David S. Miller
parent 744486d426
commit 8873c064d1
3 changed files with 5 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/net/sock.h
View File

@ -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. */

2
net/core/sock.c
View File

@ -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)
{

11
net/ipv4/tcp.c
View File

@ -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);