SUNRPC: Add rpcauth_list_flavors()

The gss_mech_list_pseudoflavors() function provides a list of
currently registered GSS pseudoflavors.  This list does not include
any non-GSS flavors that have been registered with the RPC client.
nfs4_find_root_sec() currently adds these extra flavors by hand.

Instead, nfs4_find_root_sec() should be looking at the set of flavors
that have been explicitly registered via rpcauth_register().  And,
other areas of code will soon need the same kind of list that
contains all flavors the kernel currently knows about (see below).

Rather than cloning the open-coded logic in nfs4_find_root_sec() to
those new places, introduce a generic RPC function that generates a
full list of registered auth flavors and pseudoflavors.

A new rpc_authops method is added that lists a flavor's
pseudoflavors, if it has any.  I encountered an interesting module
loader loop when I tried to get the RPC client to invoke
gss_mech_list_pseudoflavors() by name.

This patch is a pre-requisite for server trunking discovery, and a
pre-requisite for fixing up the in-kernel mount client to do better
automatic security flavor selection.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

6 files changed, 80 insertions, 9 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 31369e9b5b04..80bb5055d0b3 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -43,7 +43,6 @@
 #include <linux/printk.h>
 #include <linux/slab.h>
 #include <linux/sunrpc/clnt.h>
-#include <linux/sunrpc/gss_api.h>
 #include <linux/nfs.h>
 #include <linux/nfs4.h>
 #include <linux/nfs_fs.h>
@@ -2412,11 +2411,15 @@ static int nfs4_find_root_sec(struct nfs_server *server, struct nfs_fh *fhandle,
         int i, len, status = 0;
         rpc_authflavor_t flav_array[NFS_MAX_SECFLAVORS];
 
-        len = gss_mech_list_pseudoflavors(&flav_array[0]);
-        flav_array[len] = RPC_AUTH_NULL;
-        len += 1;
+        len = rpcauth_list_flavors(flav_array, ARRAY_SIZE(flav_array));
+        BUG_ON(len < 0);
 
         for (i = 0; i < len; i++) {
+                /* AUTH_UNIX is the default flavor if none was specified,
+                 * thus has already been tried. */
+                if (flav_array[i] == RPC_AUTH_UNIX)
+                        continue;
+
                 status = nfs4_lookup_root_sec(server, fhandle, info, flav_array[i]);
                 if (status == -NFS4ERR_WRONGSEC || status == -EACCES)
                         continue;
diff --git a/include/linux/sunrpc/auth.h b/include/linux/sunrpc/auth.h
index 492a36d72829..f25ba922baaf 100644
--- a/include/linux/sunrpc/auth.h
+++ b/include/linux/sunrpc/auth.h
@@ -101,6 +101,7 @@ struct rpc_authops {
         struct rpc_cred *       (*crcreate)(struct rpc_auth*, struct auth_cred *, int);
         int                     (*pipes_create)(struct rpc_auth *);
         void                    (*pipes_destroy)(struct rpc_auth *);
+        int                     (*list_pseudoflavors)(rpc_authflavor_t *, int);
 };
 
 struct rpc_credops {
@@ -135,6 +136,7 @@ int			rpcauth_register(const struct rpc_authops *);
 int                     rpcauth_unregister(const struct rpc_authops *);
 struct rpc_auth *       rpcauth_create(rpc_authflavor_t, struct rpc_clnt *);
 void                    rpcauth_release(struct rpc_auth *);
+int                     rpcauth_list_flavors(rpc_authflavor_t *, int);
 struct rpc_cred *       rpcauth_lookup_credcache(struct rpc_auth *, struct auth_cred *, int);
 void                    rpcauth_init_cred(struct rpc_cred *, const struct auth_cred *, struct rpc_auth *, const struct rpc_credops *);
 struct rpc_cred *       rpcauth_lookupcred(struct rpc_auth *, int);
diff --git a/include/linux/sunrpc/gss_api.h b/include/linux/sunrpc/gss_api.h
index 332da61cf8b7..a19e2547ae6a 100644
--- a/include/linux/sunrpc/gss_api.h
+++ b/include/linux/sunrpc/gss_api.h
@@ -14,6 +14,7 @@
 
 #ifdef __KERNEL__
 #include <linux/sunrpc/xdr.h>
+#include <linux/sunrpc/msg_prot.h>
 #include <linux/uio.h>
 
 /* The mechanism-independent gss-api context: */
@@ -127,7 +128,7 @@ struct gss_api_mech *gss_mech_get_by_name(const char *);
 struct gss_api_mech *gss_mech_get_by_pseudoflavor(u32);
 
 /* Fill in an array with a list of supported pseudoflavors */
-int gss_mech_list_pseudoflavors(u32 *);
+int gss_mech_list_pseudoflavors(rpc_authflavor_t *, int);
 
 /* Just increments the mechanism's reference count and returns its input: */
 struct gss_api_mech * gss_mech_get(struct gss_api_mech *);
diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c
index 727e506cacda..b5c067bccc45 100644
--- a/net/sunrpc/auth.c
+++ b/net/sunrpc/auth.c
@@ -13,6 +13,7 @@
 #include <linux/errno.h>
 #include <linux/hash.h>
 #include <linux/sunrpc/clnt.h>
+#include <linux/sunrpc/gss_api.h>
 #include <linux/spinlock.h>
 
 #ifdef RPC_DEBUG
@@ -122,6 +123,59 @@ rpcauth_unregister(const struct rpc_authops *ops)
 }
 EXPORT_SYMBOL_GPL(rpcauth_unregister);
 
+/**
+ * rpcauth_list_flavors - discover registered flavors and pseudoflavors
+ * @array: array to fill in
+ * @size: size of "array"
+ *
+ * Returns the number of array items filled in, or a negative errno.
+ *
+ * The returned array is not sorted by any policy.  Callers should not
+ * rely on the order of the items in the returned array.
+ */
+int
+rpcauth_list_flavors(rpc_authflavor_t *array, int size)
+{
+        rpc_authflavor_t flavor;
+        int result = 0;
+
+        spin_lock(&rpc_authflavor_lock);
+        for (flavor = 0; flavor < RPC_AUTH_MAXFLAVOR; flavor++) {
+                const struct rpc_authops *ops = auth_flavors[flavor];
+                rpc_authflavor_t pseudos[4];
+                int i, len;
+
+                if (result >= size) {
+                        result = -ENOMEM;
+                        break;
+                }
+
+                if (ops == NULL)
+                        continue;
+                if (ops->list_pseudoflavors == NULL) {
+                        array[result++] = ops->au_flavor;
+                        continue;
+                }
+                len = ops->list_pseudoflavors(pseudos, ARRAY_SIZE(pseudos));
+                if (len < 0) {
+                        result = len;
+                        break;
+                }
+                for (i = 0; i < len; i++) {
+                        if (result >= size) {
+                                result = -ENOMEM;
+                                break;
+                        }
+                        array[result++] = pseudos[i];
+                }
+        }
+        spin_unlock(&rpc_authflavor_lock);
+
+        dprintk("RPC:       %s returns %d\n", __func__, result);
+        return result;
+}
+EXPORT_SYMBOL_GPL(rpcauth_list_flavors);
+
 struct rpc_auth *
 rpcauth_create(rpc_authflavor_t pseudoflavor, struct rpc_clnt *clnt)
 {
diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
index d3ad81f8da5b..34c522021004 100644
--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -1619,6 +1619,7 @@ static const struct rpc_authops authgss_ops = {
         .crcreate       = gss_create_cred,
         .pipes_create   = gss_pipes_dentries_create,
         .pipes_destroy  = gss_pipes_dentries_destroy,
+        .list_pseudoflavors = gss_mech_list_pseudoflavors,
 };
 
 static const struct rpc_credops gss_credops = {
diff --git a/net/sunrpc/auth_gss/gss_mech_switch.c b/net/sunrpc/auth_gss/gss_mech_switch.c
index 782bfe1b6465..6ac5dfcd2928 100644
--- a/net/sunrpc/auth_gss/gss_mech_switch.c
+++ b/net/sunrpc/auth_gss/gss_mech_switch.c
@@ -239,14 +239,26 @@ gss_mech_get_by_pseudoflavor(u32 pseudoflavor)
 
 EXPORT_SYMBOL_GPL(gss_mech_get_by_pseudoflavor);
 
-int gss_mech_list_pseudoflavors(rpc_authflavor_t *array_ptr)
+/**
+ * gss_mech_list_pseudoflavors - Discover registered GSS pseudoflavors
+ * @array: array to fill in
+ * @size: size of "array"
+ *
+ * Returns the number of array items filled in, or a negative errno.
+ *
+ * The returned array is not sorted by any policy.  Callers should not
+ * rely on the order of the items in the returned array.
+ */
+int gss_mech_list_pseudoflavors(rpc_authflavor_t *array_ptr, int size)
 {
         struct gss_api_mech *pos = NULL;
         int j, i = 0;
 
         spin_lock(&registered_mechs_lock);
         list_for_each_entry(pos, &registered_mechs, gm_list) {
-                for (j=0; j < pos->gm_pf_num; j++) {
+                for (j = 0; j < pos->gm_pf_num; j++) {
+                        if (i >= size)
+                                return -ENOMEM;
                         array_ptr[i++] = pos->gm_pfs[j].pseudoflavor;
                 }
         }
@@ -254,8 +266,6 @@ int gss_mech_list_pseudoflavors(rpc_authflavor_t *array_ptr)
         return i;
 }
 
-EXPORT_SYMBOL_GPL(gss_mech_list_pseudoflavors);
-
 u32
 gss_svc_to_pseudoflavor(struct gss_api_mech *gm, u32 service)
 {