From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Christoph Hellwig <hch@infradead.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
xfs@oss.sgi.com
Subject: Re: inode_permission NULL pointer dereference in 3.13-rc1
Date: Fri, 29 Nov 2013 02:41:21 +0000 [thread overview]
Message-ID: <20131129024121.GS10323@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CA+55aFxLZxy75fO4ZXO4Stiu1sMx1q=eJ7HSk-UTCX61jPrirA@mail.gmail.com>
On Thu, Nov 28, 2013 at 06:07:27PM -0800, Linus Torvalds wrote:
> HOWEVER. It's certainly *not* valid if "current->fs->root/pwd" points
> to it. So yeah, there must have been an extra dput() somewhere. Or,
> more likely, I think, we don't get the refcount to some dentry
> properly any more.
>
> I don't see where, though. You did change where "LOOKUP_RCU" is
> cleared in unlazy_walk() but you did add that
>
> nd->path.dentry = NULL;
>
> and that looks like it should be ok. And I don't see what else would care.
*nod*
BTW, vfsmount refcount is 12, so we *definitely* nowhere near the
final mntput(), etc. and mnt->mnt_root itself should also have
contributed.
I'm going to try to find out _which_ test buggers the refcount - at
least that way I'll have something resembling a usable reproducer...
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WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Dave Chinner <david@fromorbit.com>,
Christoph Hellwig <hch@infradead.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
xfs@oss.sgi.com
Subject: Re: inode_permission NULL pointer dereference in 3.13-rc1
Date: Fri, 29 Nov 2013 02:41:21 +0000 [thread overview]
Message-ID: <20131129024121.GS10323@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CA+55aFxLZxy75fO4ZXO4Stiu1sMx1q=eJ7HSk-UTCX61jPrirA@mail.gmail.com>
On Thu, Nov 28, 2013 at 06:07:27PM -0800, Linus Torvalds wrote:
> HOWEVER. It's certainly *not* valid if "current->fs->root/pwd" points
> to it. So yeah, there must have been an extra dput() somewhere. Or,
> more likely, I think, we don't get the refcount to some dentry
> properly any more.
>
> I don't see where, though. You did change where "LOOKUP_RCU" is
> cleared in unlazy_walk() but you did add that
>
> nd->path.dentry = NULL;
>
> and that looks like it should be ok. And I don't see what else would care.
*nod*
BTW, vfsmount refcount is 12, so we *definitely* nowhere near the
final mntput(), etc. and mnt->mnt_root itself should also have
contributed.
I'm going to try to find out _which_ test buggers the refcount - at
least that way I'll have something resembling a usable reproducer...
next prev parent reply other threads:[~2013-11-29 2:41 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
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 [this message]
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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