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From: Christoph Hellwig <hch@infradead.org>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>,
	linux-fsdevel@vger.kernel.org, xfs@oss.sgi.com
Subject: Re: inode_permission NULL pointer dereference in 3.13-rc1
Date: Mon, 25 Nov 2013 08:06:48 -0800	[thread overview]
Message-ID: <20131125160648.GA4933@infradead.org> (raw)
In-Reply-To: <20131124152758.GL10323@ZenIV.linux.org.uk>

On Sun, Nov 24, 2013 at 03:27:58PM +0000, Al Viro wrote:
> 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?

Still reproducable with the diff below.  Fixed by reverting the RCU'd
vfsmounts.


diff --git a/fs/namei.c b/fs/namei.c
index 8f77a8c..856e4d5 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1158,6 +1158,10 @@ static int follow_dotdot_rcu(struct nameidata *nd)
 	}
 	follow_mount_rcu(nd);
 	nd->inode = nd->path.dentry->d_inode;
+
+	if (read_seqretry(&mount_lock, nd->m_seq))
+		goto failed;
+
 	return 0;
 
 failed:

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WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>,
	linux-fsdevel@vger.kernel.org, xfs@oss.sgi.com
Subject: Re: inode_permission NULL pointer dereference in 3.13-rc1
Date: Mon, 25 Nov 2013 08:06:48 -0800	[thread overview]
Message-ID: <20131125160648.GA4933@infradead.org> (raw)
In-Reply-To: <20131124152758.GL10323@ZenIV.linux.org.uk>

On Sun, Nov 24, 2013 at 03:27:58PM +0000, Al Viro wrote:
> 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?

Still reproducable with the diff below.  Fixed by reverting the RCU'd
vfsmounts.


diff --git a/fs/namei.c b/fs/namei.c
index 8f77a8c..856e4d5 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1158,6 +1158,10 @@ static int follow_dotdot_rcu(struct nameidata *nd)
 	}
 	follow_mount_rcu(nd);
 	nd->inode = nd->path.dentry->d_inode;
+
+	if (read_seqretry(&mount_lock, nd->m_seq))
+		goto failed;
+
 	return 0;
 
 failed:

  reply	other threads:[~2013-11-25 16:07 UTC|newest]

Thread overview: 48+ 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
2013-11-25 16:06   ` Christoph Hellwig [this message]
2013-11-25 16:06     ` Christoph Hellwig
2013-11-26 13:11     ` Al Viro
2013-11-26 13:11       ` Al Viro
2013-11-26 14:12       ` Christoph Hellwig
2013-11-26 14:12         ` Christoph Hellwig
2013-11-27  6:43         ` Al Viro
2013-11-27  6:43           ` Al Viro
2013-11-27 10:09           ` Christoph Hellwig
2013-11-27 10:09             ` Christoph Hellwig
2013-11-28 16:26             ` Al Viro
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
2013-11-28 23:44                     ` Al Viro
2013-11-29  1:46                     ` Dave Chinner
2013-11-29  2:07                       ` Al Viro
2013-11-29  2:07                         ` Al Viro
2013-11-29  2:17                         ` Linus Torvalds
2013-11-29  2:07                     ` Linus Torvalds
2013-11-29  2:07                       ` Linus Torvalds
2013-11-29  2:41                       ` Al Viro
2013-11-29  2:41                         ` Al Viro
2013-11-29  3:59                         ` 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  6:59                                 ` Al Viro
2013-11-29 19:44                                 ` Greg KH
2013-11-29 19:44                                   ` Greg KH
2013-11-29 20:17                                   ` Linus Torvalds
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 15:09                                   ` Theodore Ts'o
2013-11-30 15:13                                   ` Theodore Ts'o
2013-11-30 15:13                                     ` Theodore Ts'o
2013-11-27 21:51           ` Dave Chinner
2013-11-27 21:51             ` Dave Chinner
2013-11-28 15:21 ` Theodore Ts'o
2013-11-28 15:21   ` Theodore Ts'o
2013-11-28 15:36   ` Theodore Ts'o
2013-11-28 15:36     ` Theodore Ts'o

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