selinux: fix labeling of /proc/net inodes

The proc net rewrite had a side effect on selinux, leading it to mislabel
the /proc/net inodes, thereby leading to incorrect denials.  Fix
security_genfs_sid to ignore extra leading / characters in the path supplied
by selinux_proc_get_sid since we now get "//net/..." rather than "/net/...".

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>

security/selinux/ss/services.c

@@ -1744,6 +1744,9 @@ int security_genfs_sid(const char *fstype,
 	struct ocontext *c;
 	int rc = 0, cmp = 0;
 
+	while (path[0] == '/' && path[1] == '/')
+		path++;
+
 	POLICY_RDLOCK;
 
 	for (genfs = policydb.genfs; genfs; genfs = genfs->next) {