Re: [PATCH] Bluetooth: check for zapped sk before connecting
From: Marcel Holtmann <marcel@holtmann.org>
Date: 2021-03-22 15:53:53
Also in:
linux-bluetooth, lkml
Hi Archie,
quoted hunk ↗ jump to hunk
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 <redacted> Reported-by: syzbot+abfc0f5e668d4099af73@syzkaller.appspotmail.com Reviewed-by: Alain Michaud <redacted> Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org> Reviewed-by: Guenter Roeck <groeck@chromium.org> --- net/bluetooth/l2cap_sock.c | 7 +++++++ 1 file changed, 7 insertions(+)diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c index f1b1edd0b697..b86fd8cc4dc1 100644 --- a/net/bluetooth/l2cap_sock.c +++ b/net/bluetooth/l2cap_sock.c@@ -182,6 +182,13 @@ static int l2cap_sock_connect(struct socket *sock, struct sockaddr *addr,BT_DBG("sk %p", sk); + lock_sock(sk); + if (sock_flag(sk, SOCK_ZAPPED)) { + release_sock(sk); + return -EINVAL; + } + release_sock(sk); +
hmmm. I wonder if this would look better and easy to see that the locking is done correctly. lock_sock(sk); zapped = sock_flag(sk, SOCK_ZAPPED); release_sock(sk); if (zapped) return -EINVAL; Regards Marcel