From: Hillf Danton <hdanton@sina.com>
To: Amir Goldstein <amir73il@gmail.com>
Cc: syzbot <syzbot+4c493dcd5a68168a94b2@syzkaller.appspotmail.com>,
linux-fsdevel@vger.kernel.org, Al Viro <viro@zeniv.linux.org.uk>,
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
"Rafael J. Wysocki" <rafael@kernel.org>,
Pavel Machek <pavel@ucw.cz>,
linux-pm@vger.kernel.org
Subject: Re: [syzbot] [kernfs?] possible deadlock in kernfs_seq_start
Date: Fri, 10 May 2024 07:26:13 +0800 [thread overview]
Message-ID: <20240509232613.2459-1-hdanton@sina.com> (raw)
In-Reply-To: <CAOQ4uxg8karas=5JxmCg0P5Wxhfzn41evgs_OUxd1GxBRpb4zQ@mail.gmail.com>
On Thu, 9 May 2024 17:52:21 +0300 Amir Goldstein <amir73il@gmail.com>
> On Thu, May 9, 2024 at 1:49 PM Hillf Danton <hdanton@sina.com> wrote:
> >
> > The correct locking order is
> >
> > sb_writers
>
> This is sb of overlayfs
>
> > inode lock
>
> This is real inode
>
WRT sb_writers the order
lock inode parent
lock inode kid
becomes
lock inode kid
sb_writers
lock inode parent
given call trace
> -> #2 (sb_writers#4){.+.+}-{0:0}:
> lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
> percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
> __sb_start_write include/linux/fs.h:1664 [inline]
> sb_start_write+0x4d/0x1c0 include/linux/fs.h:1800
> mnt_want_write+0x3f/0x90 fs/namespace.c:409
> ovl_create_object+0x13b/0x370 fs/overlayfs/dir.c:629
> lookup_open fs/namei.c:3497 [inline]
> open_last_lookups fs/namei.c:3566 [inline]
and code snippet [1]
if (open_flag & O_CREAT)
inode_lock(dir->d_inode);
else
inode_lock_shared(dir->d_inode);
dentry = lookup_open(nd, file, op, got_write);
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/namei.c?id=dccb07f2914c#n3566
next prev parent reply other threads:[~2024-05-09 23:31 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <00000000000091228c0617eaae32@google.com>
[not found] ` <20240508231904.2259-1-hdanton@sina.com>
2024-05-09 6:37 ` [syzbot] [kernfs?] possible deadlock in kernfs_seq_start Amir Goldstein
2024-05-09 10:48 ` Hillf Danton
2024-05-09 14:52 ` Amir Goldstein
2024-05-09 23:26 ` Hillf Danton [this message]
2024-05-10 11:33 ` Hillf Danton
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