From: Stanislav Fomichev <stfomichev@gmail.com>
To: Joe Damato <jdamato@fastly.com>
Cc: netdev@vger.kernel.org, kuba@kernel.org, john.cs.hey@gmail.com,
jacob.e.keller@intel.com,
syzbot+846bb38dc67fe62cc733@syzkaller.appspotmail.com,
Tony Nguyen <anthony.l.nguyen@intel.com>,
Przemek Kitszel <przemyslaw.kitszel@intel.com>,
Andrew Lunn <andrew+netdev@lunn.ch>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Paolo Abeni <pabeni@redhat.com>,
"moderated list:INTEL ETHERNET DRIVERS"
<intel-wired-lan@lists.osuosl.org>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [Intel-wired-lan] [PATCH iwl-net] e1000: Move cancel_work_sync to avoid deadlock
Date: Fri, 30 May 2025 08:07:29 -0700 [thread overview]
Message-ID: <aDnJsSb-DNBJPNUM@mini-arch> (raw)
In-Reply-To: <20250530014949.215112-1-jdamato@fastly.com>
On 05/30, Joe Damato wrote:
> Previously, e1000_down called cancel_work_sync for the e1000 reset task
> (via e1000_down_and_stop), which takes RTNL.
>
> As reported by users and syzbot, a deadlock is possible due to lock
> inversion in the following scenario:
>
> CPU 0:
> - RTNL is held
> - e1000_close
> - e1000_down
> - cancel_work_sync (takes the work queue mutex)
> - e1000_reset_task
>
> CPU 1:
> - process_one_work (takes the work queue mutex)
> - e1000_reset_task (takes RTNL)
nit: as Jakub mentioned in another thread, it seems more about the
flush_work waiting for the reset_task to complete rather than
wq mutexes (which are fake)?
CPU 0:
- RTNL is held
- e1000_close
- e1000_down
- cancel_work_sync
- __flush_work
- <wait here for the reset_task to finish>
CPU 1:
- process_one_work
- e1000_reset_task (takes RTNL)
- <but cpu 0 already holds rtnl>
The fix looks good!
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
WARNING: multiple messages have this Message-ID (diff)
From: Stanislav Fomichev <stfomichev@gmail.com>
To: Joe Damato <jdamato@fastly.com>
Cc: netdev@vger.kernel.org, kuba@kernel.org, john.cs.hey@gmail.com,
jacob.e.keller@intel.com,
syzbot+846bb38dc67fe62cc733@syzkaller.appspotmail.com,
Tony Nguyen <anthony.l.nguyen@intel.com>,
Przemek Kitszel <przemyslaw.kitszel@intel.com>,
Andrew Lunn <andrew+netdev@lunn.ch>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Paolo Abeni <pabeni@redhat.com>,
"moderated list:INTEL ETHERNET DRIVERS"
<intel-wired-lan@lists.osuosl.org>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH iwl-net] e1000: Move cancel_work_sync to avoid deadlock
Date: Fri, 30 May 2025 08:07:29 -0700 [thread overview]
Message-ID: <aDnJsSb-DNBJPNUM@mini-arch> (raw)
In-Reply-To: <20250530014949.215112-1-jdamato@fastly.com>
On 05/30, Joe Damato wrote:
> Previously, e1000_down called cancel_work_sync for the e1000 reset task
> (via e1000_down_and_stop), which takes RTNL.
>
> As reported by users and syzbot, a deadlock is possible due to lock
> inversion in the following scenario:
>
> CPU 0:
> - RTNL is held
> - e1000_close
> - e1000_down
> - cancel_work_sync (takes the work queue mutex)
> - e1000_reset_task
>
> CPU 1:
> - process_one_work (takes the work queue mutex)
> - e1000_reset_task (takes RTNL)
nit: as Jakub mentioned in another thread, it seems more about the
flush_work waiting for the reset_task to complete rather than
wq mutexes (which are fake)?
CPU 0:
- RTNL is held
- e1000_close
- e1000_down
- cancel_work_sync
- __flush_work
- <wait here for the reset_task to finish>
CPU 1:
- process_one_work
- e1000_reset_task (takes RTNL)
- <but cpu 0 already holds rtnl>
The fix looks good!
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
next prev parent reply other threads:[~2025-05-30 15:07 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-30 1:49 [Intel-wired-lan] [PATCH iwl-net] e1000: Move cancel_work_sync to avoid deadlock Joe Damato
2025-05-30 1:49 ` Joe Damato
2025-05-30 15:07 ` Stanislav Fomichev [this message]
2025-05-30 15:07 ` Stanislav Fomichev
2025-05-30 19:45 ` [Intel-wired-lan] " Joe Damato
2025-05-30 19:45 ` Joe Damato
2025-05-31 1:31 ` [Intel-wired-lan] " Jakub Kicinski
2025-05-31 1:31 ` Jakub Kicinski
2025-06-02 20:32 ` [Intel-wired-lan] " Joe Damato
2025-06-02 20:32 ` Joe Damato
2025-06-02 21:32 ` [Intel-wired-lan] " Keller, Jacob E
2025-06-02 21:32 ` Keller, Jacob E
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