[PATCH] sunrpc: cache_register can use wrong module reference

When registering an RPC cache, cache_register() always sets the owner as the
sunrpc module.  However, there are RPC caches owned by other modules.  With
the incorrect owner setting, the real owning module can be removed potentially
with an open reference to the cache from userspace.

For example, if one were to stop the nfs server and unmount the nfsd
filesystem, the nfsd module could be removed eventhough rpc.idmapd had
references to the idtoname and nametoid caches (i.e.
/proc/net/rpc/nfs4.<cachename>/channel is still open).  This resulted in a
system panic on one of our machines when attempting to restart the nfs
services after reloading the nfsd module.

The following patch adds a 'struct module *owner' field in struct
cache_detail.  The owner is further assigned to the struct proc_dir_entry
in cache_register() so that the module cannot be unloaded while user-space
daemons have an open reference on the associated file under /proc.

Signed-off-by: Bruce Allan <bwa@us.ibm.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/nfsd/export.c

@@ -26,6 +26,7 @@
 #include <linux/namei.h>
 #include <linux/mount.h>
 #include <linux/hash.h>
+#include <linux/module.h>
 
 #include <linux/sunrpc/svc.h>
 #include <linux/nfsd/nfsd.h>
@@ -221,6 +222,7 @@ static int expkey_show(struct seq_file *m,
 }
 
 struct cache_detail svc_expkey_cache = {
+	.owner		= THIS_MODULE,
 	.hash_size	= EXPKEY_HASHMAX,
 	.hash_table	= expkey_table,
 	.name		= "nfsd.fh",
@@ -456,6 +458,7 @@ static int svc_export_show(struct seq_file *m,
 	return 0;
 }
 struct cache_detail svc_export_cache = {
+	.owner		= THIS_MODULE,
 	.hash_size	= EXPORT_HASHMAX,
 	.hash_table	= export_table,
 	.name		= "nfsd.export",

fs/nfsd/nfs4idmap.c

@@ -187,6 +187,7 @@ static int         idtoname_parse(struct cache_detail *, char *, int);
 static struct ent *idtoname_lookup(struct ent *, int);
 
 static struct cache_detail idtoname_cache = {
+	.owner		= THIS_MODULE,
 	.hash_size	= ENT_HASHMAX,
 	.hash_table	= idtoname_table,
 	.name		= "nfs4.idtoname",
@@ -320,6 +321,7 @@ static struct ent *nametoid_lookup(struct ent *, int);
 static int         nametoid_parse(struct cache_detail *, char *, int);
 
 static struct cache_detail nametoid_cache = {
+	.owner		= THIS_MODULE,
 	.hash_size	= ENT_HASHMAX,
 	.hash_table	= nametoid_table,
 	.name		= "nfs4.nametoid",
@@ -404,8 +406,10 @@ nfsd_idmap_init(void)
 void
 nfsd_idmap_shutdown(void)
 {
-	cache_unregister(&idtoname_cache);
-	cache_unregister(&nametoid_cache);
+	if (cache_unregister(&idtoname_cache))
+		printk(KERN_ERR "nfsd: failed to unregister idtoname cache\n");
+	if (cache_unregister(&nametoid_cache))
+		printk(KERN_ERR "nfsd: failed to unregister nametoid cache\n");
 }
 
 /*

include/linux/sunrpc/cache.h

@@ -60,6 +60,7 @@ struct cache_head {
 #define	CACHE_NEW_EXPIRY 120	/* keep new things pending confirmation for 120 seconds */
 
 struct cache_detail {
+	struct module *		owner;
 	int			hash_size;
 	struct cache_head **	hash_table;
 	rwlock_t		hash_lock;

net/sunrpc/auth_gss/svcauth_gss.c

@@ -250,6 +250,7 @@ static int rsi_parse(struct cache_detail *cd,
 }
 
 static struct cache_detail rsi_cache = {
+	.owner		= THIS_MODULE,
 	.hash_size	= RSI_HASHMAX,
 	.hash_table     = rsi_table,
 	.name           = "auth.rpcsec.init",
@@ -436,6 +437,7 @@ static int rsc_parse(struct cache_detail *cd,
 }
 
 static struct cache_detail rsc_cache = {
+	.owner		= THIS_MODULE,
 	.hash_size	= RSC_HASHMAX,
 	.hash_table	= rsc_table,
 	.name		= "auth.rpcsec.context",
@@ -1074,7 +1076,9 @@ gss_svc_init(void)
 void
 gss_svc_shutdown(void)
 {
-	cache_unregister(&rsc_cache);
-	cache_unregister(&rsi_cache);
+	if (cache_unregister(&rsc_cache))
+		printk(KERN_ERR "auth_rpcgss: failed to unregister rsc cache\n");
+	if (cache_unregister(&rsi_cache))
+		printk(KERN_ERR "auth_rpcgss: failed to unregister rsi cache\n");
 	svc_auth_unregister(RPC_AUTH_GSS);
 }

net/sunrpc/cache.c

@@ -177,15 +177,15 @@ void cache_register(struct cache_detail *cd)
 	cd->proc_ent = proc_mkdir(cd->name, proc_net_rpc);
 	if (cd->proc_ent) {
 		struct proc_dir_entry *p;
-		cd->proc_ent->owner = THIS_MODULE;
+		cd->proc_ent->owner = cd->owner;
 		cd->channel_ent = cd->content_ent = NULL;
 
  		p = create_proc_entry("flush", S_IFREG|S_IRUSR|S_IWUSR,
  				      cd->proc_ent);
 		cd->flush_ent =  p;
  		if (p) {
  			p->proc_fops = &cache_flush_operations;
- 			p->owner = THIS_MODULE;
+ 			p->owner = cd->owner;
  			p->data = cd;
  		}
 
@@ -195,7 +195,7 @@ void cache_register(struct cache_detail *cd)
 			cd->channel_ent = p;
 			if (p) {
 				p->proc_fops = &cache_file_operations;
-				p->owner = THIS_MODULE;
+				p->owner = cd->owner;
 				p->data = cd;
 			}
 		}
@@ -205,7 +205,7 @@ void cache_register(struct cache_detail *cd)
 			cd->content_ent = p;
  			if (p) {
  				p->proc_fops = &content_file_operations;
- 				p->owner = THIS_MODULE;
+ 				p->owner = cd->owner;
  				p->data = cd;
  			}
  		}

net/sunrpc/sunrpc_syms.c

@@ -176,8 +176,10 @@ cleanup_sunrpc(void)
 {
 	unregister_rpc_pipefs();
 	rpc_destroy_mempool();
-	cache_unregister(&auth_domain_cache);
-	cache_unregister(&ip_map_cache);
+	if (cache_unregister(&auth_domain_cache))
+		printk(KERN_ERR "sunrpc: failed to unregister auth_domain cache\n");
+	if (cache_unregister(&ip_map_cache))
+		printk(KERN_ERR "sunrpc: failed to unregister ip_map cache\n");
 #ifdef RPC_DEBUG
 	rpc_unregister_sysctl();
 #endif

net/sunrpc/svcauth.c

@@ -143,6 +143,7 @@ static void auth_domain_drop(struct cache_head *item, struct cache_detail *cd)
 
 
 struct cache_detail auth_domain_cache = {
+	.owner		= THIS_MODULE,
 	.hash_size	= DN_HASHMAX,
 	.hash_table	= auth_domain_table,
 	.name		= "auth.domain",

net/sunrpc/svcauth_unix.c

@@ -242,6 +242,7 @@ static int ip_map_show(struct seq_file *m,
 
 
 struct cache_detail ip_map_cache = {
+	.owner		= THIS_MODULE,
 	.hash_size	= IP_HASHMAX,
 	.hash_table	= ip_table,
 	.name		= "auth.unix.ip",