From: Al Viro <viro@ZenIV.linux.org.uk>
To: Christoph Hellwig <hch@infradead.org>
Cc: linux-fsdevel@vger.kernel.org, xfs@oss.sgi.com
Subject: Re: inode_permission NULL pointer dereference in 3.13-rc1
Date: Sun, 24 Nov 2013 15:27:58 +0000 [thread overview]
Message-ID: <20131124152758.GL10323@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20131124140413.GA19271@infradead.org>
On Sun, Nov 24, 2013 at 06:04:13AM -0800, Christoph Hellwig wrote:
> Seems I can reproduce this by doing a full xfstests run and then
> shutting down the VM. Doesn't seem to happen with the XFS tree
> which is still based on 3.12-rc1.
may_lookup() with LOOKUP_RCU in nd->flags and NULL nd->inode, by
the look of it... Interesting.
AFAICS, path_init() initializes nd->inode on all success exits.
As for the places where we reassign nd->inode, we have the following:
fs/namei.c:681: nd->inode = nd->path.dentry->d_inode;
nd_jump_link(), we would've already left RCU mode
fs/namei.c:856: nd->inode = nd->path.dentry->d_inode;
follow_link() - ditto.
fs/namei.c:1160: nd->inode = nd->path.dentry->d_inode;
follow_dotdot_rcu()
fs/namei.c:1257: nd->inode = nd->path.dentry->d_inode;
follow_dotdot() - not in RCU mode
fs/namei.c:1547: nd->inode = inode;
walk_component() - inode can't be NULL here, variable has
been explicitly compared with NULL a few lines prior
fs/namei.c:1825: nd->inode = inode;
path_init() with LOOKUP_ROOT; not from stat(2) and it would've
already oopsed with NULL inode anyway.
fs/namei.c:1892: nd->inode = nd->path.dentry->d_inode;
path_init()
fs/namei.c:3006: nd->inode = inode;
do_last(), not from stat(2) and no may_lookup() done past that
point anyway.
fs/namei.c:3077: nd->inode = dir->d_inode;
do_last(), not from stat(2)
which seems to leave two candidates - follow_dotdot_rcu() and path_init(),
both setting nd->inode to nd->path.dentry->d_inode...
Could you try to reproduce it with something like
if (read_seqretry(&mount_lock, nd->m_seq))
goto failed;
slapped before the success exit in follow_dotdot_rcu(), just to see if
we are hitting some races with umount here?
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next prev parent reply other threads:[~2013-11-24 15:27 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-24 14:04 inode_permission NULL pointer dereference in 3.13-rc1 Christoph Hellwig
2013-11-24 15:27 ` Al Viro [this message]
2013-11-25 16:06 ` Christoph Hellwig
2013-11-26 13:11 ` Al Viro
2013-11-26 14:12 ` Christoph Hellwig
2013-11-27 6:43 ` Al Viro
2013-11-27 10:09 ` Christoph Hellwig
2013-11-28 16:26 ` Al Viro
2013-11-28 21:23 ` Al Viro
2013-11-28 22:51 ` Dave Chinner
2013-11-28 23:44 ` Al Viro
2013-11-29 1:46 ` Dave Chinner
2013-11-29 2:07 ` Al Viro
2013-11-29 2:17 ` Linus Torvalds
2013-11-29 2:07 ` Linus Torvalds
2013-11-29 2:41 ` Al Viro
2013-11-29 3:59 ` Al Viro
2013-11-29 4:06 ` Al Viro
2013-11-29 4:14 ` Al Viro
2013-11-29 6:59 ` Al Viro
2013-11-29 19:44 ` Greg KH
2013-11-29 20:17 ` Linus Torvalds
2013-11-29 23:55 ` Al Viro
2013-11-30 0:18 ` Linus Torvalds
2013-11-30 15:09 ` [GIT PULL] " Theodore Ts'o
2013-11-30 15:13 ` Theodore Ts'o
2013-11-27 21:51 ` Dave Chinner
2013-11-28 15:21 ` Theodore Ts'o
2013-11-28 15:36 ` Theodore Ts'o
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