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Date:   Tue, 23 Mar 2021 16:32:20 +0800
Message-Id: <20210323163141.v2.1.I6c4306f6e8ba3ccc9106067d4eb70092f8cb2a49@changeid>
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Subject: [PATCH v2] Bluetooth: check for zapped sk before connecting
From:   Archie Pusaka <apusaka@google.com>
To:     linux-bluetooth <linux-bluetooth@vger.kernel.org>,
        Marcel Holtmann <marcel@holtmann.org>
Cc:     CrosBT Upstreaming <chromeos-bluetooth-upstreaming@chromium.org>,
        Archie Pusaka <apusaka@chromium.org>,
        syzbot+abfc0f5e668d4099af73@syzkaller.appspotmail.com,
        Alain Michaud <alainm@chromium.org>,
        Abhishek Pandit-Subedi <abhishekpandit@chromium.org>,
        Guenter Roeck <groeck@chromium.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org
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From: Archie Pusaka <apusaka@chromium.org>

There is a possibility of receiving a zapped sock on
l2cap_sock_connect(). This could lead to interesting crashes, one
such case is tearing down an already tore l2cap_sock as is happened
with this call trace:

__dump_stack lib/dump_stack.c:15 [inline]
dump_stack+0xc4/0x118 lib/dump_stack.c:56
register_lock_class kernel/locking/lockdep.c:792 [inline]
register_lock_class+0x239/0x6f6 kernel/locking/lockdep.c:742
__lock_acquire+0x209/0x1e27 kernel/locking/lockdep.c:3105
lock_acquire+0x29c/0x2fb kernel/locking/lockdep.c:3599
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:137 [inline]
_raw_spin_lock_bh+0x38/0x47 kernel/locking/spinlock.c:175
spin_lock_bh include/linux/spinlock.h:307 [inline]
lock_sock_nested+0x44/0xfa net/core/sock.c:2518
l2cap_sock_teardown_cb+0x88/0x2fb net/bluetooth/l2cap_sock.c:1345
l2cap_chan_del+0xa3/0x383 net/bluetooth/l2cap_core.c:598
l2cap_chan_close+0x537/0x5dd net/bluetooth/l2cap_core.c:756
l2cap_chan_timeout+0x104/0x17e net/bluetooth/l2cap_core.c:429
process_one_work+0x7e3/0xcb0 kernel/workqueue.c:2064
worker_thread+0x5a5/0x773 kernel/workqueue.c:2196
kthread+0x291/0x2a6 kernel/kthread.c:211
ret_from_fork+0x4e/0x80 arch/x86/entry/entry_64.S:604

Signed-off-by: Archie Pusaka <apusaka@chromium.org>
Reported-by: syzbot+abfc0f5e668d4099af73@syzkaller.appspotmail.com
Reviewed-by: Alain Michaud <alainm@chromium.org>
Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
---

Changes in v2:
* Modify locking order for better visibility

 net/bluetooth/l2cap_sock.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index f1b1edd0b697..c99d65ef13b1 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -179,9 +179,17 @@ static int l2cap_sock_connect(struct socket *sock, struct sockaddr *addr,
 	struct l2cap_chan *chan = l2cap_pi(sk)->chan;
 	struct sockaddr_l2 la;
 	int len, err = 0;
+	bool zapped;
 
 	BT_DBG("sk %p", sk);
 
+	lock_sock(sk);
+	zapped = sock_flag(sk, SOCK_ZAPPED);
+	release_sock(sk);
+
+	if (zapped)
+		return -EINVAL;
+
 	if (!addr || alen < offsetofend(struct sockaddr, sa_family) ||
 	    addr->sa_family != AF_BLUETOOTH)
 		return -EINVAL;
-- 
2.31.0.291.g576ba9dcdaf-goog