linux-kernel - utimes() with vfat is problematic

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Date:	Tue, 10 Jul 2007 11:47:43 +0200 (CEST)
From:	Jan Engelhardt <jengelh@...putergmbh.de>
To:	linux-fsdevel@...r.kernel.org
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	hirofumi@...l.parknet.co.jp
Subject: utimes() with vfat is problematic

Hi,



vfat does not know about ownership, hence the files are always owned by the
vfat mounter (or whatever the uid= option specified). Which brings 
a problem to userspace programs trying to utime() but which do not 
run as the same user as the vfat mounter, because:


fs/attr.c:53
	ret = -EPERM;
	[...]

	/* Check for setting the inode time. */
	if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET)) {
		if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
                        goto error;
        }


To trigger the problem:
	# mount /somevfat -o umask=0,uid=root
	$ touch -d "2005-05-05" /somevfat/myfile

I am not sure how this could be dealt with besides passing -o quiet to 
mount.vfat. Any ideas?



	Jan
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