svcrpc: store gss mech in svc_cred

Store a pointer to the gss mechanism used in the rq_cred and cl_cred.
This will make it easier to enforce SP4_MACH_CRED, which needs to
compare the mechanism used on the exchange_id with that used on
protected operations.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

include/linux/sunrpc/gss_api.h

@@ -151,6 +151,8 @@ 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(rpc_authflavor_t *, int);
 
+struct gss_api_mech * gss_mech_get(struct gss_api_mech *);
+
 /* For every successful gss_mech_get or gss_mech_get_by_* call there must be a
  * corresponding call to gss_mech_put. */
 void gss_mech_put(struct gss_api_mech *);

include/linux/sunrpc/svcauth.h

@@ -14,6 +14,7 @@
 #include <linux/string.h>
 #include <linux/sunrpc/msg_prot.h>
 #include <linux/sunrpc/cache.h>
+#include <linux/sunrpc/gss_api.h>
 #include <linux/hash.h>
 #include <linux/cred.h>
 
@@ -23,6 +24,7 @@ struct svc_cred {
 	struct group_info	*cr_group_info;
 	u32			cr_flavor; /* pseudoflavor */
 	char			*cr_principal; /* for gss */
+	struct gss_api_mech	*cr_gss_mech;
 };
 
 static inline void init_svc_cred(struct svc_cred *cred)
@@ -37,6 +39,8 @@ static inline void free_svc_cred(struct svc_cred *cred)
 	if (cred->cr_group_info)
 		put_group_info(cred->cr_group_info);
 	kfree(cred->cr_principal);
+	gss_mech_put(cred->cr_gss_mech);
+	init_svc_cred(cred);
 }
 
 struct svc_rqst;		/* forward decl */