[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>

5 files changed, 16 insertions, 8 deletions

diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index 5c8fe3bfc494..e3308195374e 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -250,6 +250,7 @@ out:
 }
 
 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 @@ out:
 }
 
 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);
 }
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 900f5bc7e336..f509e9992767 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -177,7 +177,7 @@ 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,
@@ -185,7 +185,7 @@ void cache_register(struct cache_detail *cd)
                 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;
                         }
                 }
diff --git a/net/sunrpc/sunrpc_syms.c b/net/sunrpc/sunrpc_syms.c
index 62a073495276..ed48ff022d35 100644
--- a/net/sunrpc/sunrpc_syms.c
+++ b/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
diff --git a/net/sunrpc/svcauth.c b/net/sunrpc/svcauth.c
index bde8147ef2db..dda4f0c63511 100644
--- a/net/sunrpc/svcauth.c
+++ b/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",
diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
index d6baf6fdf8a9..cac2e774dd81 100644
--- a/net/sunrpc/svcauth_unix.c
+++ b/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",