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%3Ba=su...

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