[PATCH 20/25] sysfs: Rename Support multiple superblocks

Eric W. Biederman ebiederm at xmission.com
Wed Aug 8 09:55:10 PDT 2007

Tejun Heo <htejun at gmail.com> writes:

> Eric W. Biederman wrote:
>>> 	/* Find the first parent which has valid dentry.
>>> 	 */
>>> 	dentry = NULL;
>>> 	cur = sd;
>>> 	while (!(dentry = __sysfs_get_dentry(sb, cur))) {
>>> 		if (cur->s_flags & SYSFS_FLAG_REMOVED) {
>>> 			dentry = ERR_PTR(-ENOENT);
>>> 			break;
>>> 		}
>>> 		cur = cur->s_parent;
>>> 	}
>> Here we depend on the fact that sysfs_root is pointed to
>> by sb->s_root so we know it will always have a dentry.
> Hmmm... dentry could be ERR_PTR(-ENOENT) here if the REMOVED flag test
> succeeded, right?

Ugh right.  Now that I don't have the locking it probably makes
sense to have that path just return or branch to the exit.

>>> 	/* from the found dentry, look up depth times */
>>> 	while (dentry->d_fsdata != sd) {
> And then dereferenced.  The REMOVED test should never succeed there, so
> we're probably in the clear but still the code looks a bit scary.

Agreed.  That is a bug.  Either the removed test needs to
be removed because it can't happen or that case needs to be handled.

Thanks for spotting this one.

Mental blind spots are the worst.


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