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Bluetooth: Fix possible deadlock in rfcomm_sk_state_change

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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: 1804fdf6e4 ("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>
This commit is contained in:
Ying Hsu 2023-01-11 03:16:14 +00:00 committed by Luiz Augusto von Dentz
parent 506d9b4099
commit 1d80d57ffc
1 changed files with 6 additions and 1 deletions
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7
net/bluetooth/rfcomm/sock.c
View File

@ -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;
}