Patch "kcm: lock lower socket in kcm_attach" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    kcm: lock lower socket in kcm_attach

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     kcm-lock-lower-socket-in-kcm_attach.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Wed Mar 28 20:16:33 CEST 2018
From: Tom Herbert <tom@quantonium.net>
Date: Tue, 13 Mar 2018 12:01:43 -0700
Subject: kcm: lock lower socket in kcm_attach

From: Tom Herbert <tom@quantonium.net>


[ Upstream commit 2cc683e88c0c993ac3721d9b702cb0630abe2879 ]

Need to lock lower socket in order to provide mutual exclusion
with kcm_unattach.

v2: Add Reported-by for syzbot

Fixes: ab7ac4eb9832e32a09f4e804 ("kcm: Kernel Connection Multiplexor module")
Reported-by: syzbot+ea75c0ffcd353d32515f064aaebefc5279e6161e@syzkaller.appspotmail.com
Signed-off-by: Tom Herbert <tom@quantonium.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/kcm/kcmsock.c |   33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)

--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -1375,24 +1375,32 @@ static int kcm_attach(struct socket *soc
 	struct list_head *head;
 	int index = 0;
 	struct strp_callbacks cb;
-	int err;
+	int err = 0;
 
 	csk = csock->sk;
 	if (!csk)
 		return -EINVAL;
 
+	lock_sock(csk);
+
 	/* Only allow TCP sockets to be attached for now */
 	if ((csk->sk_family != AF_INET && csk->sk_family != AF_INET6) ||
-	    csk->sk_protocol != IPPROTO_TCP)
-		return -EOPNOTSUPP;
+	    csk->sk_protocol != IPPROTO_TCP) {
+		err = -EOPNOTSUPP;
+		goto out;
+	}
 
 	/* Don't allow listeners or closed sockets */
-	if (csk->sk_state == TCP_LISTEN || csk->sk_state == TCP_CLOSE)
-		return -EOPNOTSUPP;
+	if (csk->sk_state == TCP_LISTEN || csk->sk_state == TCP_CLOSE) {
+		err = -EOPNOTSUPP;
+		goto out;
+	}
 
 	psock = kmem_cache_zalloc(kcm_psockp, GFP_KERNEL);
-	if (!psock)
-		return -ENOMEM;
+	if (!psock) {
+		err = -ENOMEM;
+		goto out;
+	}
 
 	psock->mux = mux;
 	psock->sk = csk;
@@ -1406,7 +1414,7 @@ static int kcm_attach(struct socket *soc
 	err = strp_init(&psock->strp, csk, &cb);
 	if (err) {
 		kmem_cache_free(kcm_psockp, psock);
-		return err;
+		goto out;
 	}
 
 	write_lock_bh(&csk->sk_callback_lock);
@@ -1418,7 +1426,8 @@ static int kcm_attach(struct socket *soc
 		write_unlock_bh(&csk->sk_callback_lock);
 		strp_done(&psock->strp);
 		kmem_cache_free(kcm_psockp, psock);
-		return -EALREADY;
+		err = -EALREADY;
+		goto out;
 	}
 
 	psock->save_data_ready = csk->sk_data_ready;
@@ -1454,7 +1463,10 @@ static int kcm_attach(struct socket *soc
 	/* Schedule RX work in case there are already bytes queued */
 	strp_check_rcv(&psock->strp);
 
-	return 0;
+out:
+	release_sock(csk);
+
+	return err;
 }
 
 static int kcm_attach_ioctl(struct socket *sock, struct kcm_attach *info)
@@ -1506,6 +1518,7 @@ static void kcm_unattach(struct kcm_psoc
 
 	if (WARN_ON(psock->rx_kcm)) {
 		write_unlock_bh(&csk->sk_callback_lock);
+		release_sock(csk);
 		return;
 	}
 


Patches currently in stable-queue which might be from tom@quantonium.net are

queue-4.9/kcm-lock-lower-socket-in-kcm_attach.patch