From 9db7e5fffbaecfa76aae285bf3e6c8cd4535897c Mon Sep 17 00:00:00 2001 From: Pauli Virtanen Date: Sun, 9 Aug 2026 01:06:05 +0300 Subject: Bluetooth: L2CAP: reject accept queue add unless BT_LISTEN New sk should not be added to parent socket accept queue after last l2cap_sock_cleanup_listen() has run in l2cap_sock_teardown_cb() and state set to BT_CLOSED, as that can result to UAF on dereferencing the dangling parent reference. l2cap_sock_new_connection_cb() may race with parent l2cap_chan teardown, due to chan->state accessed without consistent locking: [Task 1] [Task 2] l2cap_sock_release(parent) l2cap_connect l2cap_sock_shutdown pchan = l2cap_global_chan_by_psm l2cap_chan_lock(pchan) l2cap_chan_close l2cap_sock_teardown_cb pchan->state = BT_CLOSED l2cap_chan_unlock(pchan) ------> l2cap_chan_lock(pchan) l2cap_new_connection l2cap_sock_new_connection_cb l2cap_chan_lock(pchan) <-------- l2cap_chan_unlock(pchan) l2cap_sock_kill(parent) /* bt_sk(sk)->parent dangling */ Fix by adding check for sk_state == BT_LISTEN after acquiring sk lock in l2cap_sock_new_connection_cb(). Add lock_sock() around sk_state writes where missing, to avoid data races. Although the data races on pchan->state should be fixed too, this defensive sk_state check probably makes sense in any case. Fixes: 2ff1a41a912d ("Bluetooth: L2CAP: Fix null-ptr-deref in l2cap_sock_state_change_cb()") Reported-by: syzbot+9265e754091c2d27ea29@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=9265e754091c2d27ea29 Signed-off-by: Pauli Virtanen Reported-by: syzbot+9265e754091c2d27ea29@syzkaller.appspotmail.com Tested-by: syzbot+9265e754091c2d27ea29@syzkaller.appspotmail.com Signed-off-by: Luiz Augusto von Dentz --- net/bluetooth/l2cap_sock.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c index cca6201f9cdb..8bf35bc8126f 100644 --- a/net/bluetooth/l2cap_sock.c +++ b/net/bluetooth/l2cap_sock.c @@ -1600,6 +1600,11 @@ static int l2cap_sock_new_connection_cb(struct l2cap_chan *chan, lock_sock(parent); + if (parent->sk_state != BT_LISTEN) { + release_sock(parent); + return -EINVAL; + } + /* Check for backlog size */ if (sk_acceptq_is_full(parent)) { BT_DBG("backlog full %d", parent->sk_ack_backlog); @@ -1763,10 +1768,14 @@ static void l2cap_sock_state_change_cb(struct l2cap_chan *chan, int state, if (!sk) return; + lock_sock(sk); + sk->sk_state = state; if (err) sk->sk_err = err; + + release_sock(sk); } static struct sk_buff *l2cap_sock_alloc_skb_cb(struct l2cap_chan *chan, @@ -1842,6 +1851,8 @@ static void l2cap_sock_resume_cb(struct l2cap_chan *chan) if (!sk) return; + lock_sock(sk); + if (test_and_clear_bit(FLAG_PENDING_SECURITY, &chan->flags)) { sk->sk_state = BT_CONNECTED; chan->state = BT_CONNECTED; @@ -1849,6 +1860,8 @@ static void l2cap_sock_resume_cb(struct l2cap_chan *chan) clear_bit(BT_SK_SUSPEND, &bt_sk(sk)->flags); sk->sk_state_change(sk); + + release_sock(sk); } static void l2cap_sock_set_shutdown_cb(struct l2cap_chan *chan) -- cgit v1.2.3