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From: Al Viro <viro@ZenIV.linux.org.uk>
To: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	linux-fsdevel@vger.kernel.org,
	Linus Torvalds <torvalds@linux-foundation.org>,
	xfs@oss.sgi.com
Subject: Re: inode_permission NULL pointer dereference in 3.13-rc1
Date: Fri, 29 Nov 2013 02:07:03 +0000	[thread overview]
Message-ID: <20131129020703.GR10323@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20131129014648.GU10988@dastard>

On Fri, Nov 29, 2013 at 12:46:48PM +1100, Dave Chinner wrote:
> > 	* d_count(dentry) is -128
> 
> void lockref_mark_dead(struct lockref *lockref)
> {
>         assert_spin_locked(&lockref->lock);
>         lockref->count = -128;
> }

... done once refcount reaches zero and we decide to evict the sucker.
Which, for dentry that happens to be
	* pwd of at least one process
	* root of at least one process
	* root dentry of a filesystem that contains at least one
binary being executed
means that we have dropped several references too many.  Thus the
comment about unbalanced dput() somewhere; the question is _where_ had
that dput() been.

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WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	linux-fsdevel@vger.kernel.org,
	Linus Torvalds <torvalds@linux-foundation.org>,
	xfs@oss.sgi.com
Subject: Re: inode_permission NULL pointer dereference in 3.13-rc1
Date: Fri, 29 Nov 2013 02:07:03 +0000	[thread overview]
Message-ID: <20131129020703.GR10323@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20131129014648.GU10988@dastard>

On Fri, Nov 29, 2013 at 12:46:48PM +1100, Dave Chinner wrote:
> > 	* d_count(dentry) is -128
> 
> void lockref_mark_dead(struct lockref *lockref)
> {
>         assert_spin_locked(&lockref->lock);
>         lockref->count = -128;
> }

... done once refcount reaches zero and we decide to evict the sucker.
Which, for dentry that happens to be
	* pwd of at least one process
	* root of at least one process
	* root dentry of a filesystem that contains at least one
binary being executed
means that we have dropped several references too many.  Thus the
comment about unbalanced dput() somewhere; the question is _where_ had
that dput() been.

  reply	other threads:[~2013-11-29  2:07 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
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 [this message]
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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