tree cdb15adf5fe5c201c87d17c7847cf07484d8a441
parent 3c9fe8cdff1b889a059a30d22f130372f2b3885f
author Miklos Szeredi <mszeredi@redhat.com> 1462922197 +0200
committer Al Viro <viro@zeniv.linux.org.uk> 1462939098 -0400

ovl: ignore permissions on underlying lookup

Generally permission checking is not necessary when overlayfs looks up a
dentry on one of the underlying layers, since search permission on base
directory was already checked in ovl_permission().

More specifically using lookup_one_len() causes a problem when the lower
directory lacks search permission for a specific user while the upper
directory does have search permission.  Since lookups are cached, this
causes inconsistency in behavior: success depends on who did the first
lookup.

So instead use lookup_hash() which doesn't do the permission check.

Reported-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>