Commit a8b897c7 authored by Paolo Abeni's avatar Paolo Abeni Committed by David S. Miller
Browse files

udp: fix race between close() and udp_abort() 



Kaustubh reported and diagnosed a panic in udp_lib_lookup().
The root cause is udp_abort() racing with close(). Both
racing functions acquire the socket lock, but udp{v6}_destroy_sock()
release it before performing destructive actions.

We can't easily extend the socket lock scope to avoid the race,
instead use the SOCK_DEAD flag to prevent udp_abort from doing
any action when the critical race happens.

Diagnosed-and-tested-by: default avatarKaustubh Pandey <kapandey@codeaurora.org>
Fixes: 5d77dca8 ("net: diag: support SOCK_DESTROY for UDP sockets")
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent dcd01eea

net/ipv4/udp.c

+10 −0
Original line number Diff line number Diff line
@@ -2607,6 +2607,9 @@ void udp_destroy_sock(struct sock *sk) 
{

	struct udp_sock *up = udp_sk(sk);

	bool slow = lock_sock_fast(sk);



	/* protects from races with udp_abort() */

	sock_set_flag(sk, SOCK_DEAD);

	udp_flush_pending_frames(sk);

	unlock_sock_fast(sk, slow);

	if (static_branch_unlikely(&udp_encap_needed_key)) {
@@ -2857,10 +2860,17 @@ int udp_abort(struct sock *sk, int err) 
{

	lock_sock(sk);



	/* udp{v6}_destroy_sock() sets it under the sk lock, avoid racing

	 * with close()

	 */

	if (sock_flag(sk, SOCK_DEAD))

		goto out;



	sk->sk_err = err;

	sk->sk_error_report(sk);

	__udp_disconnect(sk, 0);



out:

	release_sock(sk);



	return 0;

net/ipv6/udp.c

+3 −0
Original line number Diff line number Diff line
@@ -1598,6 +1598,9 @@ void udpv6_destroy_sock(struct sock *sk) 
{

	struct udp_sock *up = udp_sk(sk);

	lock_sock(sk);



	/* protects from races with udp_abort() */

	sock_set_flag(sk, SOCK_DEAD);

	udp_v6_flush_pending_frames(sk);

	release_sock(sk);