From 1d80d57ffcb55488f0ec0b77928d4f82d16b6a90 Mon Sep 17 00:00:00 2001
From: Ying Hsu <yinghsu@chromium.org>
Date: Wed, 11 Jan 2023 03:16:14 +0000
Subject: [PATCH] Bluetooth: Fix possible deadlock in rfcomm_sk_state_change
Git-commit: 1d80d57ffcb55488f0ec0b77928d4f82d16b6a90
Patch-mainline: v6.2-rc5
References: git-fixes
syzbot reports a possible deadlock in rfcomm_sk_state_change [1].
While rfcomm_sock_connect acquires the sk lock and waits for
the rfcomm lock, rfcomm_sock_release could have the rfcomm
lock and hit a deadlock for acquiring the sk lock.
Here's a simplified flow:
Rfcomm_sock_connect: lock_sock(sk) rfcomm_dlc_open: rfcomm_lock()
Rfcomm_sock_release: rfcomm_sock_shutdown: rfcomm_lock() __rfcomm_dlc_close: rfcomm_k_state_change: lock_sock(sk)
This patch drops the sk lock before calling rfcomm_dlc_open to
avoid the possible deadlock and holds sk's reference count to
prevent use-after-free after rfcomm_dlc_open completes.
Reported-by: syzbot+d7ce59...@syzkaller.appspotmail.com
Fixes: 1804fdf6e494 ("Bluetooth: btintel: Combine setting up MSFT extension")
Link: https://syzkaller.appspot.com/bug?extid=d7ce59b06b3eb14fd218 [1]
Signed-off-by: Ying Hsu <yinghsu@chromium.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
net/bluetooth/rfcomm/sock.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
index 21e24da4847f..4397e14ff560 100644
--- a/net/bluetooth/rfcomm/sock.c
+++ b/net/bluetooth/rfcomm/sock.c
@@ -391,6 +391,7 @@ static int rfcomm_sock_connect(struct socket *sock, struct sockaddr *addr, int a
addr->sa_family != AF_BLUETOOTH)
return -EINVAL;
+ sock_hold(sk);
lock_sock(sk);
if (sk->sk_state != BT_OPEN && sk->sk_state != BT_BOUND) {
@@ -410,14 +411,18 @@ static int rfcomm_sock_connect(struct socket *sock, struct sockaddr *addr, int a
d->sec_level = rfcomm_pi(sk)->sec_level;
d->role_switch = rfcomm_pi(sk)->role_switch;
+ /* Drop sock lock to avoid potential deadlock with the RFCOMM lock */
+ release_sock(sk);
err = rfcomm_dlc_open(d, &rfcomm_pi(sk)->src, &sa->rc_bdaddr,
sa->rc_channel);
- if (!err)
+ lock_sock(sk);
+ if (!err && !sock_flag(sk, SOCK_ZAPPED))
err = bt_sock_wait_state(sk, BT_CONNECTED,
sock_sndtimeo(sk, flags & O_NONBLOCK));
done:
release_sock(sk);
+ sock_put(sk);
return err;
}
--
2.35.3