[PATCH] kNFSd: gss_svc locking and refcounting fixes

The server sunrpc code should take a reference on the relevant module before
calling any authentication code.

Also, it looks to me like the table of authops needs some locking.

Finally, gss_svc_init wasn't checking the status of svc_auth_register, and
gss_svc_shutdown wasn't calling svc_auth_unregister.

From: "J. Bruce Fields" <bfields@fieldses.org>
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/sunrpc/svcauth.h

@@ -87,6 +87,7 @@ struct auth_domain {
  */
 struct auth_ops {
 	char *	name;
+	struct module *owner;
 	int	flavour;
 	int	(*accept)(struct svc_rqst *rq, u32 *authp);
 	int	(*release)(struct svc_rqst *rq);

net/sunrpc/auth_gss/svcauth_gss.c

@@ -1045,6 +1045,7 @@ svcauth_gss_domain_release(struct auth_domain *dom)
 
 struct auth_ops svcauthops_gss = {
 	.name		= "rpcsec_gss",
+	.owner		= THIS_MODULE,
 	.flavour	= RPC_AUTH_GSS,
 	.accept		= svcauth_gss_accept,
 	.release	= svcauth_gss_release,
@@ -1054,10 +1055,12 @@ struct auth_ops svcauthops_gss = {
 int
 gss_svc_init(void)
 {
-	cache_register(&rsc_cache);
-	cache_register(&rsi_cache);
-	svc_auth_register(RPC_AUTH_GSS, &svcauthops_gss);
-	return 0;
+	int rv = svc_auth_register(RPC_AUTH_GSS, &svcauthops_gss);
+	if (rv == 0) {
+		cache_register(&rsc_cache);
+		cache_register(&rsi_cache);
+	}
+	return rv;
 }
 
 void
@@ -1065,4 +1068,5 @@ gss_svc_shutdown(void)
 {
 	cache_unregister(&rsc_cache);
 	cache_unregister(&rsi_cache);
+	svc_auth_unregister(RPC_AUTH_GSS);
 }

net/sunrpc/svcauth.c

@@ -11,6 +11,7 @@
 
 #include <linux/types.h>
 #include <linux/sched.h>
+#include <linux/module.h>
 #include <linux/sunrpc/types.h>
 #include <linux/sunrpc/xdr.h>
 #include <linux/sunrpc/svcsock.h>
@@ -27,6 +28,7 @@
 extern struct auth_ops svcauth_null;
 extern struct auth_ops svcauth_unix;
 
+static spinlock_t authtab_lock = SPIN_LOCK_UNLOCKED;
 static struct auth_ops	*authtab[RPC_AUTH_MAXFLAVOR] = {
 	[0] = &svcauth_null,
 	[1] = &svcauth_unix,
@@ -43,10 +45,15 @@ svc_authenticate(struct svc_rqst *rqstp, u32 *authp)
 	flavor = ntohl(svc_getu32(&rqstp->rq_arg.head[0]));
 
 	dprintk("svc: svc_authenticate (%d)\n", flavor);
-	if (flavor >= RPC_AUTH_MAXFLAVOR || !(aops = authtab[flavor])) {
+
+	spin_lock(&authtab_lock);
+	if (flavor >= RPC_AUTH_MAXFLAVOR || !(aops = authtab[flavor])
+			|| !try_module_get(aops->owner)) {
+		spin_unlock(&authtab_lock);
 		*authp = rpc_autherr_badcred;
 		return SVC_DENIED;
 	}
+	spin_unlock(&authtab_lock);
 
 	rqstp->rq_authop = aops;
 	return aops->accept(rqstp, authp);
@@ -63,28 +70,35 @@ int svc_authorise(struct svc_rqst *rqstp)
 
 	rqstp->rq_authop = NULL;
 	
-	if (aops) 
+	if (aops) {
 		rv = aops->release(rqstp);
-
-	/* FIXME should I count and release authops */
+		module_put(aops->owner);
+	}
 	return rv;
 }
 
 int
 svc_auth_register(rpc_authflavor_t flavor, struct auth_ops *aops)
 {
-	if (flavor >= RPC_AUTH_MAXFLAVOR || authtab[flavor])
-		return -EINVAL;
-	authtab[flavor] = aops;
-	return 0;
+	int rv = -EINVAL;
+	spin_lock(&authtab_lock);
+	if (flavor < RPC_AUTH_MAXFLAVOR && authtab[flavor] == NULL) {
+		authtab[flavor] = aops;
+		rv = 0;
+	}
+	spin_unlock(&authtab_lock);
+	return rv;
 }
 
 void
 svc_auth_unregister(rpc_authflavor_t flavor)
 {
+	spin_lock(&authtab_lock);
 	if (flavor < RPC_AUTH_MAXFLAVOR)
 		authtab[flavor] = NULL;
+	spin_unlock(&authtab_lock);
 }
+EXPORT_SYMBOL(svc_auth_unregister);
 
 /**************************************************
  * cache for domain name to auth_domain

net/sunrpc/svcauth_unix.c

 #include <linux/types.h>
 #include <linux/sched.h>
+#include <linux/module.h>
 #include <linux/sunrpc/types.h>
 #include <linux/sunrpc/xdr.h>
 #include <linux/sunrpc/svcsock.h>
@@ -411,6 +412,7 @@ svcauth_null_release(struct svc_rqst *rqstp)
 
 struct auth_ops svcauth_null = {
 	.name		= "null",
+	.owner		= THIS_MODULE,
 	.flavour	= RPC_AUTH_NULL,
 	.accept 	= svcauth_null_accept,
 	.release	= svcauth_null_release,
@@ -515,6 +517,7 @@ svcauth_unix_release(struct svc_rqst *rqstp)
 
 struct auth_ops svcauth_unix = {
 	.name		= "unix",
+	.owner		= THIS_MODULE,
 	.flavour	= RPC_AUTH_UNIX,
 	.accept 	= svcauth_unix_accept,
 	.release	= svcauth_unix_release,