sunrpc: svcauth_gss_register_pseudoflavor must reject duplicate registrations.

commit d47a5dc2888fd1b94adf1553068b8dad76cec96c upstream.

There is no valid case for supporting duplicate pseudoflavor
registrations.
Currently the silent acceptance of such registrations is hiding a bug.
The rpcsec_gss_krb5 module registers 2 flavours but does not unregister
them, so if you load, unload, reload the module, it will happily
continue to use the old registration which now has pointers to the
memory were the module was originally loaded.  This could lead to
unexpected results.

So disallow duplicate registrations.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=206651
Cc: stable@vger.kernel.org (v2.6.12+)
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index a457e7afb7688c628395f5596d348a640d5f3f5f..af17e02a021cba3d619dc66a8e5cc46488df3de2 100644 (file)
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -796,9 +796,11 @@ svcauth_gss_register_pseudoflavor(u32 pseudoflavor, char * name)
        new->h.flavour = &svcauthops_gss;
        new->pseudoflavor = pseudoflavor;
 
-       stat = 0;
        test = auth_domain_lookup(name, &new->h);
-       if (test != &new->h) { /* Duplicate registration */
+       if (test != &new->h) {
+               pr_warn("svc: duplicate registration of gss pseudo flavour %s.\n",
+                       name);
+               stat = -EADDRINUSE;
                auth_domain_put(test);
                kfree(new->h.name);
                goto out_free_dom;