[syzbot] possible deadlock in rfcomm_sk_state_change

[syzbot] possible deadlock in rfcomm_sk_state_change

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    a3fa7a101dcf Merge branches 'akpm' and 'akpm-hotfixes' (pa..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10d61a8b300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a9b60f3b657f313d
dashboard link: https://syzkaller.appspot.com/bug?extid=d7ce59b06b3eb14fd218
compiler:       Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15247a7d300000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12a2642b300000

The issue was bisected to:

commit 1804fdf6e494e5e2938c65d8391690b59bcff897
Author: Tedd Ho-Jeong An <tedd.an@intel.com>
Date:   Thu Aug 5 00:32:19 2021 +0000

    Bluetooth: btintel: Combine setting up MSFT extension

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=125f4163300000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=115f4163300000
console output: https://syzkaller.appspot.com/x/log.txt?x=165f4163300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d7ce59b06b3eb14fd218@syzkaller.appspotmail.com
Fixes: 1804fdf6e494 ("Bluetooth: btintel: Combine setting up MSFT extension")

======================================================
WARNING: possible circular locking dependency detected
5.14.0-syzkaller #0 Not tainted
------------------------------------------------------
krfcommd/2875 is trying to acquire lock:
ffff888012b9d120 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1612 [inline]
ffff888012b9d120 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sk_state_change+0x63/0x300 net/bluetooth/rfcomm/sock.c:73

but task is already holding lock:
ffff88807cf12528 (&d->lock){+.+.}-{3:3}, at: __rfcomm_dlc_close+0x281/0x480 net/bluetooth/rfcomm/core.c:487

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&d->lock){+.+.}-{3:3}:
       lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5625
       __mutex_lock_common+0x1df/0x2550 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:743
       __rfcomm_dlc_close+0x281/0x480 net/bluetooth/rfcomm/core.c:487
       rfcomm_process_dlcs+0x92/0x620 net/bluetooth/rfcomm/core.c:1844
       rfcomm_process_sessions+0x2f6/0x3f0 net/bluetooth/rfcomm/core.c:2003
       rfcomm_run+0x195/0x2c0 net/bluetooth/rfcomm/core.c:2086
       kthread+0x453/0x480 kernel/kthread.c:319
       ret_from_fork+0x1f/0x30

-> #1 (rfcomm_mutex){+.+.}-{3:3}:
       lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5625
       __mutex_lock_common+0x1df/0x2550 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:743
       rfcomm_dlc_open+0x25/0x50 net/bluetooth/rfcomm/core.c:425
       rfcomm_sock_connect+0x285/0x470 net/bluetooth/rfcomm/sock.c:413
       __sys_connect_file net/socket.c:1896 [inline]
       __sys_connect+0x38a/0x410 net/socket.c:1913
       __do_sys_connect net/socket.c:1923 [inline]
       __se_sys_connect net/socket.c:1920 [inline]
       __x64_sys_connect+0x76/0x80 net/socket.c:1920
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3051 [inline]
       check_prevs_add kernel/locking/lockdep.c:3174 [inline]
       validate_chain+0x1dfb/0x8240 kernel/locking/lockdep.c:3789
       __lock_acquire+0x1382/0x2b00 kernel/locking/lockdep.c:5015
       lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5625
       lock_sock_nested+0xc6/0x110 net/core/sock.c:3191
       lock_sock include/net/sock.h:1612 [inline]
       rfcomm_sk_state_change+0x63/0x300 net/bluetooth/rfcomm/sock.c:73
       __rfcomm_dlc_close+0x2cc/0x480 net/bluetooth/rfcomm/core.c:489
       rfcomm_process_dlcs+0x92/0x620 net/bluetooth/rfcomm/core.c:1844
       rfcomm_process_sessions+0x2f6/0x3f0 net/bluetooth/rfcomm/core.c:2003
       rfcomm_run+0x195/0x2c0 net/bluetooth/rfcomm/core.c:2086
       kthread+0x453/0x480 kernel/kthread.c:319
       ret_from_fork+0x1f/0x30

other info that might help us debug this:

Chain exists of:
  sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM --> rfcomm_mutex --> &d->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&d->lock);
                               lock(rfcomm_mutex);
                               lock(&d->lock);
  lock(sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM);

 *** DEADLOCK ***

2 locks held by krfcommd/2875:
 #0: ffffffff8dac7488 (rfcomm_mutex){+.+.}-{3:3}, at: rfcomm_process_sessions+0x21/0x3f0 net/bluetooth/rfcomm/core.c:1979
 #1: ffff88807cf12528 (&d->lock){+.+.}-{3:3}, at: __rfcomm_dlc_close+0x281/0x480 net/bluetooth/rfcomm/core.c:487

stack backtrace:
CPU: 1 PID: 2875 Comm: krfcommd Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1dc/0x2d8 lib/dump_stack.c:106
 check_noncircular+0x2f9/0x3b0 kernel/locking/lockdep.c:2131
 check_prev_add kernel/locking/lockdep.c:3051 [inline]
 check_prevs_add kernel/locking/lockdep.c:3174 [inline]
 validate_chain+0x1dfb/0x8240 kernel/locking/lockdep.c:3789
 __lock_acquire+0x1382/0x2b00 kernel/locking/lockdep.c:5015
 lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5625
 lock_sock_nested+0xc6/0x110 net/core/sock.c:3191
 lock_sock include/net/sock.h:1612 [inline]
 rfcomm_sk_state_change+0x63/0x300 net/bluetooth/rfcomm/sock.c:73
 __rfcomm_dlc_close+0x2cc/0x480 net/bluetooth/rfcomm/core.c:489
 rfcomm_process_dlcs+0x92/0x620 net/bluetooth/rfcomm/core.c:1844
 rfcomm_process_sessions+0x2f6/0x3f0 net/bluetooth/rfcomm/core.c:2003
 rfcomm_run+0x195/0x2c0 net/bluetooth/rfcomm/core.c:2086
 kthread+0x453/0x480 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30


---
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Re: [syzbot] Re: [PATCH v1] Bluetooth: RFCOMM: FIX possible deadlock in rfcomm_sk_state_change

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: Re: [PATCH v1] Bluetooth: RFCOMM: FIX possible deadlock in rfcomm_sk_state_change
Author: luiz.dentz@gmail.com

#syz test

On Mon, Sep 30, 2024 at 4:36 PM Luiz Augusto von Dentz
<luiz.dentz@gmail.com> wrote:
>
> On Mon, Sep 30, 2024 at 3:30 PM Luiz Augusto von Dentz
> <luiz.dentz@gmail.com> wrote:
> >
> > From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> >
> > rfcomm_sk_state_change attempts to use sock_lock so it must never be
> > called with it locked but rfcomm_sock_ioctl always attempt to lock it
> > causing the following trace:
> >
> > ======================================================
> > WARNING: possible circular locking dependency detected
> > 6.8.0-syzkaller-08951-gfe46a7dd189e #0 Not tainted
> > ------------------------------------------------------
> > syz-executor386/5093 is trying to acquire lock:
> > ffff88807c396258 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1671 [inline]
> > ffff88807c396258 (sk_lock-AF_BLUETOOTH-BTPROTO_RFCOMM){+.+.}-{0:0}, at: rfcomm_sk_state_change+0x5b/0x310 net/bluetooth/rfcomm/sock.c:73
> >
> > but task is already holding lock:
> > ffff88807badfd28 (&d->lock){+.+.}-{3:3}, at: __rfcomm_dlc_close+0x226/0x6a0 net/bluetooth/rfcomm/core.c:491
> >
> > Reported-by: syzbot+d7ce59b06b3eb14fd218@syzkaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=d7ce59b06b3eb14fd218
> > Fixes: 3241ad820dbb ("[Bluetooth] Add timestamp support to L2CAP, RFCOMM and SCO")
> > Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> > ---
> >  net/bluetooth/rfcomm/sock.c | 2 --
> >  1 file changed, 2 deletions(-)
> >
> > diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
> > index 37d63d768afb..f48250e3f2e1 100644
> > --- a/net/bluetooth/rfcomm/sock.c
> > +++ b/net/bluetooth/rfcomm/sock.c
> > @@ -865,9 +865,7 @@ static int rfcomm_sock_ioctl(struct socket *sock, unsigned int cmd, unsigned lon
> >
> >         if (err == -ENOIOCTLCMD) {
> >  #ifdef CONFIG_BT_RFCOMM_TTY
> > -               lock_sock(sk);
> >                 err = rfcomm_dev_ioctl(sk, cmd, (void __user *) arg);
> > -               release_sock(sk);
> >  #else
> >                 err = -EOPNOTSUPP;
> >  #endif
> > --
> > 2.46.1
> >
>
>
> --
> Luiz Augusto von Dentz



-- 
Luiz Augusto von Dentz