netdev - [PATCH] af_unix: check socket state when queuing OOB

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Date:   Fri, 13 Aug 2021 11:19:34 -0700
From:   Rao Shoaib <Rao.Shoaib@...cle.com>
To:     netdev@...r.kernel.org, kuba@...nel.org, rao.shoaib@...cle.com,
        viro@...iv.linux.org.uk, edumazet@...gle.com
Subject: [PATCH] af_unix: check socket state when queuing OOB

edumazet@...gle.com pointed out that queue_oob
does not check socket state after acquiring
the lock. He also pointed to an incorrect usage
of kfree_skb and an unnecessary setting of skb
length. This patch addresses those issue.

Signed-off-by: Rao Shoaib <Rao.Shoaib@...cle.com>
---
 net/unix/af_unix.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index a626e52c629a..0f59fed993d8 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1891,7 +1891,6 @@ static int queue_oob(struct socket *sock, struct msghdr *msg, struct sock *other
 		return err;
 
 	skb_put(skb, 1);
-	skb->len = 1;
 	err = skb_copy_datagram_from_iter(skb, 0, &msg->msg_iter, 1);
 
 	if (err) {
@@ -1900,11 +1899,19 @@ static int queue_oob(struct socket *sock, struct msghdr *msg, struct sock *other
 	}
 
 	unix_state_lock(other);
+
+	if (sock_flag(other, SOCK_DEAD) ||
+	    (other->sk_shutdown & RCV_SHUTDOWN)) {
+		unix_state_unlock(other);
+		kfree_skb(skb);
+		return -EPIPE;
+	}
+
 	maybe_add_creds(skb, sock, other);
 	skb_get(skb);
 
 	if (ousk->oob_skb)
-		kfree_skb(ousk->oob_skb);
+		consume_skb(ousk->oob_skb);
 
 	ousk->oob_skb = skb;
 
-- 
2.27.0