This is a note to let you know that I've just added the patch titled
Bluetooth: RFCOMM: FIX possible deadlock in rfcomm_sk_state_change
to the 4.19-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:
bluetooth-rfcomm-fix-possible-deadlock-in-rfcomm_sk_.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 4dd4d2d7c091dd321be9b4381fd15e7e07759530
Author: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx>
Date: Mon Sep 30 13:26:21 2024 -0400
Bluetooth: RFCOMM: FIX possible deadlock in rfcomm_sk_state_change
[ Upstream commit 08d1914293dae38350b8088980e59fbc699a72fe ]
rfcomm_sk_state_change attempts to use sock_lock so it must never be
called with it locked but rfcomm_sock_ioctl always attempt to lock it
causing the following trace:
======================================================
WARNING: possible circular locking dependency detected
6.8.0-syzkaller-08951-gfe46a7dd189e #0 Not tainted
------------------------------------------------------
syz-executor386/5093 is trying to acquire lock:
ffff88807c396258 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1671 [inline]
ffff88807c396258 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sk_state_change+0x5b/0x310 net/bluetooth/rfcomm/sock.c:73
but task is already holding lock:
ffff88807badfd28 (&d->lock){+.+.}-{3:3}, at: __rfcomm_dlc_close+0x226/0x6a0 net/bluetooth/rfcomm/core.c:491
Reported-by: syzbot+d7ce59b06b3eb14fd218@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested-by: syzbot+d7ce59b06b3eb14fd218@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=d7ce59b06b3eb14fd218
Fixes: 3241ad820dbb ("[Bluetooth] Add timestamp support to L2CAP, RFCOMM and SCO")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
index 78830efe89d73..8f53cc0d9682a 100644
--- a/net/bluetooth/rfcomm/sock.c
+++ b/net/bluetooth/rfcomm/sock.c
@@ -872,9 +872,7 @@ static int rfcomm_sock_ioctl(struct socket *sock, unsigned int cmd, unsigned lon
if (err == -ENOIOCTLCMD) {
#ifdef CONFIG_BT_RFCOMM_TTY
- lock_sock(sk);
err = rfcomm_dev_ioctl(sk, cmd, (void __user *) arg);
- release_sock(sk);
#else
err = -EOPNOTSUPP;
#endif
