Re: [PATCH v15 2/9] namei: LOOKUP_NO_MAGICLINKS: block magic-link resolution

Al Viro
2019-11-13T01:27:08Z

On Tue, Nov 05, 2019 at 08:05:46PM +1100, Aleksa Sarai wrote:
> @@ -1078,6 +1079,10 @@ const char *get_link(struct nameidata *nd)
> } else {
> res = get(dentry, inode, &last->done);
> }
> + if (nd->flags & LOOKUP_MAGICLINK_JUMPED) {
> + if (unlikely(nd->flags & LOOKUP_NO_MAGICLINKS))
> + return ERR_PTR(-ELOOP);
> + }

Minor nit - the first check probably wants unlikely() more than the
second one; it's probably noise anyway, but most of the symlinks
traversed are not going to be procfs ones, so you get test + branch
taken most of the time.

OTOH, that just might compile into
fetch nd->flags
and with LOOKUP_MAGICLINK_JUMPED | LOOKUP_NO_MAGICLINKS
compare with the same constant
unlikely branch when equal

Anyway, that's no more than a minor nit and can be dealt with later (if
at all)