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From: Dave Chinner <david@fromorbit.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Dave Jones <davej@redhat.com>,
	Linux Kernel <linux-kernel@vger.kernel.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	xfs@oss.sgi.com
Subject: Re: fs/attr.c:notify_change locking warning.
Date: Wed, 16 Oct 2013 21:26:51 +1100	[thread overview]
Message-ID: <20131016102651.GF4446@dastard> (raw)
In-Reply-To: <20131016070528.GB18721@infradead.org>

On Wed, Oct 16, 2013 at 12:05:28AM -0700, Christoph Hellwig wrote:
> On Wed, Oct 16, 2013 at 08:36:18AM +1100, Dave Chinner wrote:
> > Sure, but file_remove_suid() doesn't actually modify any VFS inode
> > structures until we process the flags and the modifications within
> > ->setattr, which in XFS are all done under the XFS_ILOCK_EXCL via
> > xfs_setattr_mode(). i.e. both the VFS and XFS inodes S*ID bits are
> > removed only under XFS_ILOCK_EXCL....
> 
> It can set S_NOSEC after calling into ->setattr at least.
> 
> > Hence I see no point in adding extra serialisation via the i_mutex
> > to this path when we can just do something like:
> > 
> > 	killsuid = should_remove_suid(file->f_path.dentry);
> > 	if (killsuid) {
> > 		struct iattr	newattr;
> > 
> > 		newattr.ia_valid = ATTR_FORCE | killsuid;
> > 		error = xfs_setattr_nonsize(ip, &newattr, 0);
> > 		if (error)
> > 			return error;
> > 	}
> 
> We'd still need all the other magic in file_remove_suid, which I don't
> actually quite undersdtand fully yet.

The killpriv calls? I couldn't find anything that implemented those
security hooks nor any documentation about it, so I'm pretty much
clueless about it. FWIW, ocfs2 doesn't implement them, either....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david@fromorbit.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Dave Jones <davej@redhat.com>,
	xfs@oss.sgi.com, Linux Kernel <linux-kernel@vger.kernel.org>,
	Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: fs/attr.c:notify_change locking warning.
Date: Wed, 16 Oct 2013 21:26:51 +1100	[thread overview]
Message-ID: <20131016102651.GF4446@dastard> (raw)
In-Reply-To: <20131016070528.GB18721@infradead.org>

On Wed, Oct 16, 2013 at 12:05:28AM -0700, Christoph Hellwig wrote:
> On Wed, Oct 16, 2013 at 08:36:18AM +1100, Dave Chinner wrote:
> > Sure, but file_remove_suid() doesn't actually modify any VFS inode
> > structures until we process the flags and the modifications within
> > ->setattr, which in XFS are all done under the XFS_ILOCK_EXCL via
> > xfs_setattr_mode(). i.e. both the VFS and XFS inodes S*ID bits are
> > removed only under XFS_ILOCK_EXCL....
> 
> It can set S_NOSEC after calling into ->setattr at least.
> 
> > Hence I see no point in adding extra serialisation via the i_mutex
> > to this path when we can just do something like:
> > 
> > 	killsuid = should_remove_suid(file->f_path.dentry);
> > 	if (killsuid) {
> > 		struct iattr	newattr;
> > 
> > 		newattr.ia_valid = ATTR_FORCE | killsuid;
> > 		error = xfs_setattr_nonsize(ip, &newattr, 0);
> > 		if (error)
> > 			return error;
> > 	}
> 
> We'd still need all the other magic in file_remove_suid, which I don't
> actually quite undersdtand fully yet.

The killpriv calls? I couldn't find anything that implemented those
security hooks nor any documentation about it, so I'm pretty much
clueless about it. FWIW, ocfs2 doesn't implement them, either....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

  reply	other threads:[~2013-10-16 10:27 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-10-05  0:52 fs/attr.c:notify_change locking warning Dave Jones
2013-10-05  0:52 ` Dave Jones
2013-10-05  3:19 ` Dave Chinner
2013-10-05  3:19   ` Dave Chinner
2013-10-15 20:19   ` Christoph Hellwig
2013-10-15 20:19     ` Christoph Hellwig
2013-10-15 21:36     ` Dave Chinner
2013-10-15 21:36       ` Dave Chinner
2013-10-16  7:05       ` Christoph Hellwig
2013-10-16  7:05         ` Christoph Hellwig
2013-10-16 10:26         ` Dave Chinner [this message]
2013-10-16 10:26           ` Dave Chinner
2013-10-16 18:12           ` Christoph Hellwig
2013-10-16 18:12             ` Christoph Hellwig

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