netdev.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Leon Romanovsky <leon@kernel.org>
To: Saeed Mahameed <saeed@kernel.org>
Cc: Ying Hsu <yinghsu@chromium.org>,
	linux-bluetooth@vger.kernel.org,
	chromeos-bluetooth-upstreaming@chromium.org,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Johan Hedberg <johan.hedberg@gmail.com>,
	Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
	Marcel Holtmann <marcel@holtmann.org>,
	Paolo Abeni <pabeni@redhat.com>,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH] Bluetooth: Fix possible deadlock in rfcomm_sk_state_change
Date: Sun, 8 Jan 2023 12:12:49 +0200	[thread overview]
Message-ID: <Y7qXIZNsju8dCzqu@unreal> (raw)
In-Reply-To: <Y7dqKnQe8UUeQ/CD@x130>

On Thu, Jan 05, 2023 at 04:24:10PM -0800, Saeed Mahameed wrote:
> On 04 Jan 08:51, Leon Romanovsky wrote:
> > On Tue, Jan 03, 2023 at 11:12:46AM +0000, Ying Hsu wrote:
> > > There's a possible deadlock when two processes are connecting
> > > and closing concurrently:
> > >   + CPU0: __rfcomm_dlc_close locks rfcomm and then calls
> > >   rfcomm_sk_state_change which locks the sock.
> > >   + CPU1: rfcomm_sock_connect locks the socket and then calls
> > >   rfcomm_dlc_open which locks rfcomm.
> > > 
> > > Here's the call trace:
> > > 
> > > -> #2 (&d->lock){+.+.}-{3:3}:
> > >        __mutex_lock_common kernel/locking/mutex.c:603 [inline]
> > >        __mutex_lock0x12f/0x1360 kernel/locking/mutex.c:747
> > >        __rfcomm_dlc_close+0x15d/0x890 net/bluetooth/rfcomm/core.c:487
> > >        rfcomm_dlc_close+1e9/0x240 net/bluetooth/rfcomm/core.c:520
> > >        __rfcomm_sock_close+0x13c/0x250 net/bluetooth/rfcomm/sock.c:220
> > >        rfcomm_sock_shutdown+0xd8/0x230 net/bluetooth/rfcomm/sock.c:907
> > >        rfcomm_sock_release+0x68/0x140 net/bluetooth/rfcomm/sock.c:928
> > >        __sock_release+0xcd/0x280 net/socket.c:650
> > >        sock_close+0x1c/0x20 net/socket.c:1365
> > >        __fput+0x27c/0xa90 fs/file_table.c:320
> > >        task_work_run+0x16f/0x270 kernel/task_work.c:179
> > >        exit_task_work include/linux/task_work.h:38 [inline]
> > >        do_exit+0xaa8/0x2950 kernel/exit.c:867
> > >        do_group_exit+0xd4/0x2a0 kernel/exit.c:1012
> > >        get_signal+0x21c3/0x2450 kernel/signal.c:2859
> > >        arch_do_signal_or_restart+0x79/0x5c0 arch/x86/kernel/signal.c:306
> > >        exit_to_user_mode_loop kernel/entry/common.c:168 [inline]
> > >        exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:203
> > >        __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
> > >        syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:296
> > >        do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86
> > >        entry_SYSCALL_64_after_hwframe+0x63/0xcd
> > > 
> > > -> #1 (rfcomm_mutex){+.+.}-{3:3}:
> > >        __mutex_lock_common kernel/locking/mutex.c:603 [inline]
> > >        __mutex_lock+0x12f/0x1360 kernel/locking/mutex.c:747
> > >        rfcomm_dlc_open+0x93/0xa80 net/bluetooth/rfcomm/core.c:425
> > >        rfcomm_sock_connect+0x329/0x450 net/bluetooth/rfcomm/sock.c:413
> > >        __sys_connect_file+0x153/0x1a0 net/socket.c:1976
> > >        __sys_connect+0x165/0x1a0 net/socket.c:1993
> > >        __do_sys_connect net/socket.c:2003 [inline]
> > >        __se_sys_connect net/socket.c:2000 [inline]
> > >        __x64_sys_connect+0x73/0xb0 net/socket.c:2000
> > >        do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> > >        do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
> > >        entry_SYSCALL_64_after_hwframe+0x63/0xcd
> > > 
> > > -> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}:
> > >        check_prev_add kernel/locking/lockdep.c:3097 [inline]
> > >        check_prevs_add kernel/locking/lockdep.c:3216 [inline]
> > >        validate_chain kernel/locking/lockdep.c:3831 [inline]
> > >        __lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5055
> > >        lock_acquire kernel/locking/lockdep.c:5668 [inline]
> > >        lock_acquire+0x1e3/0x630 kernel/locking/lockdep.c:5633
> > >        lock_sock_nested+0x3a/0xf0 net/core/sock.c:3470
> > >        lock_sock include/net/sock.h:1725 [inline]
> > >        rfcomm_sk_state_change+0x6d/0x3a0 net/bluetooth/rfcomm/sock.c:73
> > >        __rfcomm_dlc_close+0x1b1/0x890 net/bluetooth/rfcomm/core.c:489
> > >        rfcomm_dlc_close+0x1e9/0x240 net/bluetooth/rfcomm/core.c:520
> > >        __rfcomm_sock_close+0x13c/0x250 net/bluetooth/rfcomm/sock.c:220
> > >        rfcomm_sock_shutdown+0xd8/0x230 net/bluetooth/rfcomm/sock.c:907
> > >        rfcomm_sock_release+0x68/0x140 net/bluetooth/rfcomm/sock.c:928
> > >        __sock_release+0xcd/0x280 net/socket.c:650
> > >        sock_close+0x1c/0x20 net/socket.c:1365
> > >        __fput+0x27c/0xa90 fs/file_table.c:320
> > >        task_work_run+0x16f/0x270 kernel/task_work.c:179
> > >        exit_task_work include/linux/task_work.h:38 [inline]
> > >        do_exit+0xaa8/0x2950 kernel/exit.c:867
> > >        do_group_exit+0xd4/0x2a0 kernel/exit.c:1012
> > >        get_signal+0x21c3/0x2450 kernel/signal.c:2859
> > >        arch_do_signal_or_restart+0x79/0x5c0 arch/x86/kernel/signal.c:306
> > >        exit_to_user_mode_loop kernel/entry/common.c:168 [inline]
> > >        exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:203
> > >        __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
> > >        syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:296
> > >        do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86
> > >        entry_SYSCALL_64_after_hwframe+0x63/0xcd
> > > 
> > > Signed-off-by: Ying Hsu <yinghsu@chromium.org>
> > > ---
> > > This commit has been tested with a C reproducer on qemu-x86_64.
> > > 
> > >  net/bluetooth/rfcomm/sock.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > > 
> > > diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
> > > index 21e24da4847f..29f9a88a3dc8 100644
> > > --- a/net/bluetooth/rfcomm/sock.c
> > > +++ b/net/bluetooth/rfcomm/sock.c
> > > @@ -410,8 +410,10 @@ 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;
> > > 
> > > +	release_sock(sk);
> > >  	err = rfcomm_dlc_open(d, &rfcomm_pi(sk)->src, &sa->rc_bdaddr,
> >                                           ^^^^
> > Are you sure that "sk" still exists here after you called to release_sock(sk)?
> > What prevents from use-after-free here?
> > 
> 
> sk must be valid to be locked in first place.

It is, but after it is released it won't.

> release_sock() has mutex unlock semantics so it doesn't free anything..

What do you mean?

I see a lot of magic release calls.

  3481 void release_sock(struct sock *sk)
  3482 {
  3483         spin_lock_bh(&sk->sk_lock.slock);
  3484         if (sk->sk_backlog.tail)
  3485                 __release_sock(sk);
  3486
  3487         /* Warning : release_cb() might need to release sk ownership,
  3488          * ie call sock_release_ownership(sk) before us.
  3489          */
  3490         if (sk->sk_prot->release_cb)
  3491                 sk->sk_prot->release_cb(sk);
  3492
  3493         sock_release_ownership(sk);
  3494         if (waitqueue_active(&sk->sk_lock.wq))
  3495                 wake_up(&sk->sk_lock.wq);
  3496         spin_unlock_bh(&sk->sk_lock.slock);
  3497 }
  3498 EXPORT_SYMBOL(release_sock);

Thanks

  reply	other threads:[~2023-01-08 10:13 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-03 11:12 [PATCH] Bluetooth: Fix possible deadlock in rfcomm_sk_state_change Ying Hsu
2023-01-04  6:51 ` Leon Romanovsky
2023-01-06  0:24   ` Saeed Mahameed
2023-01-08 10:12     ` Leon Romanovsky [this message]
2023-01-10  9:07       ` Saeed Mahameed
2023-01-10 12:22         ` Leon Romanovsky
2023-01-11  1:03           ` Saeed Mahameed
2023-01-11  0:34         ` Luiz Augusto von Dentz
2023-01-11  0:50           ` Saeed Mahameed

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=Y7qXIZNsju8dCzqu@unreal \
    --to=leon@kernel.org \
    --cc=chromeos-bluetooth-upstreaming@chromium.org \
    --cc=davem@davemloft.net \
    --cc=edumazet@google.com \
    --cc=johan.hedberg@gmail.com \
    --cc=kuba@kernel.org \
    --cc=linux-bluetooth@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=luiz.dentz@gmail.com \
    --cc=marcel@holtmann.org \
    --cc=netdev@vger.kernel.org \
    --cc=pabeni@redhat.com \
    --cc=saeed@kernel.org \
    --cc=yinghsu@chromium.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).