Commit a07dd890 authored Jul 19, 2021 by Paolo Abeni Committed by Yang Yingliang Jul 19, 2021

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



stable inclusion
from linux-4.19.196
commit 2f73448041bd0682d4b552cfd314ace66107f1ad

--------------------------------

[ Upstream commit a8b897c7 ]

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: Kaustubh Pandey <kapandey@codeaurora.org>
Fixes: 5d77dca8 ("net: diag: support SOCK_DESTROY for UDP sockets")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>

parent 37bf8e62

net/ipv4/udp.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -2429,6 +2429,9 @@ 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) && up->encap_type) {
		@@ -2670,10 +2673,17 @@ 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
		@@ -1476,6 +1476,9 @@ 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);