From: Paolo Abeni pabeni@redhat.com
[ Upstream commit a8b897c7bcd47f4147d066e22cc01d1026d7640e ]
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: 5d77dca82839 ("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 --- net/ipv4/udp.c | 10 ++++++++++ net/ipv6/udp.c | 3 +++ 2 files changed, 13 insertions(+)
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index 24841a9e9966..4644f86c932f 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -2511,6 +2511,9 @@ 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)) { @@ -2770,10 +2773,17 @@ 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; diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 6762430280f5..3c94b81bb459 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -1539,6 +1539,9 @@ 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);