Re: [patch] Fix block device inode list corruptions

[viro@parcelfarce.linux.theplanet.co.uk]

On Wed, Feb 04, 2004 at 03:27:44PM +0000, Stephen C. Tweedie wrote:
> Hi,
> 
> I've been chasing a weird SELinux bug which shows up mostly when doing
> installs of a dev-* rpm (ie. creating and overwriting lots of block
> device inodes), but which I've also seen when doing mkinitrd.
> 
> It turned out not to be an SELinux problem at all, but a core VFS
> S_ISBLK bug.  It seems that SELinux simply widens the race window.
> 
> The code at fault is fs/fs-writeback.c:__mark_inode_dirty():
> 
> 		/*
> 		 * Only add valid (hashed) inodes to the superblock's
> 		 * dirty list.  Add blockdev inodes as well.
> 		 */
> 		if (!S_ISBLK(inode->i_mode)) {
> 			if (hlist_unhashed(&inode->i_hash))
> 				goto out;
> 			if (inode->i_state & (I_FREEING|I_CLEAR))
> 				goto out;
> 		}
> 
> The "I_FREEING|I_CLEAR" condition was added after the ISBLK/unhashed
> tests were already in the source, but I can't see any reason why we'd
> want the I_FREEING test not to apply to block devices.  And indeed, this
> results in all sorts of inode list corruptions.  Simply moving the
> I_FREEING|I_CLEAR test out of the protection of the S_ISBLK() condition
> fixes things entirely.  

ACK.