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Date: Mon, 3 Feb 2020 16:20:42 +0000 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, syzbot+eba992608adf3d796bcc@...kaller.appspotmail.com, Dan Carpenter <dan.carpenter@...cle.com>, Johan Hedberg <johan.hedberg@...el.com> Subject: [PATCH 5.5 22/23] Bluetooth: Fix race condition in hci_release_sock() From: Dan Carpenter <dan.carpenter@...cle.com> commit 11eb85ec42dc8c7a7ec519b90ccf2eeae9409de8 upstream. Syzbot managed to trigger a use after free "KASAN: use-after-free Write in hci_sock_bind". I have reviewed the code manually and one possibly cause I have found is that we are not holding lock_sock(sk) when we do the hci_dev_put(hdev) in hci_sock_release(). My theory is that the bind and the release are racing against each other which results in this use after free. Reported-by: syzbot+eba992608adf3d796bcc@...kaller.appspotmail.com Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com> Signed-off-by: Johan Hedberg <johan.hedberg@...el.com> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- net/bluetooth/hci_sock.c | 3 +++ 1 file changed, 3 insertions(+) --- a/net/bluetooth/hci_sock.c +++ b/net/bluetooth/hci_sock.c @@ -831,6 +831,8 @@ static int hci_sock_release(struct socke if (!sk) return 0; + lock_sock(sk); + switch (hci_pi(sk)->channel) { case HCI_CHANNEL_MONITOR: atomic_dec(&monitor_promisc); @@ -878,6 +880,7 @@ static int hci_sock_release(struct socke skb_queue_purge(&sk->sk_receive_queue); skb_queue_purge(&sk->sk_write_queue); + release_sock(sk); sock_put(sk); return 0; }
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