linux-kernel - [PATCH v3 0/2] fcntl: fix potential deadlocks

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Date:   Wed,  7 Jul 2021 15:43:59 +0800
From:   Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>
To:     jlayton@...nel.org, bfields@...ldses.org, viro@...iv.linux.org.uk
Cc:     Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        skhan@...uxfoundation.org, gregkh@...uxfoundation.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: [PATCH v3 0/2] fcntl: fix potential deadlocks

Hi,

Sorry for the delay between v1 and v2, there was an unrelated issue with Syzbot testing.

Syzbot reports a possible irq lock inversion dependency:
https://syzkaller.appspot.com/bug?id=923cfc6c6348963f99886a0176ef11dcc429547b

While investigating this error, I discovered that multiple similar lock inversion scenarios can occur. Hence, this series addresses potential deadlocks for two classes of locks, one in each patch:

1. Fix potential deadlocks for &fown_struct.lock

2. Fix potential deadlock for &fasync_struct.fa_lock

v2 -> v3:
- Removed WARN_ON_ONCE, keeping elaboration for why read_lock_irq is safe to use in the commit message. As suggested by Greg KH.

v1 -> v2:
- Added WARN_ON_ONCE(irqs_disabled()) before calls to read_lock_irq, and added elaboration in the commit message. As suggested by Jeff Layton.

Best wishes,
Desmond

Desmond Cheong Zhi Xi (2):
  fcntl: fix potential deadlocks for &fown_struct.lock
  fcntl: fix potential deadlock for &fasync_struct.fa_lock

 fs/fcntl.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

-- 
2.25.1