proc 2/2: remove struct proc_dir_entry::owner

Setting ->owner as done currently (pde->owner = THIS_MODULE) is racy
as correctly noted at bug #12454. Someone can lookup entry with NULL
->owner, thus not pinning enything, and release it later resulting
in module refcount underflow.

We can keep ->owner and supply it at registration time like ->proc_fops
and ->data.

But this leaves ->owner as easy-manipulative field (just one C assignment)
and somebody will forget to unpin previous/pin current module when
switching ->owner. ->proc_fops is declared as "const" which should give
some thoughts.

->read_proc/->write_proc were just fixed to not require ->owner for
protection.

rmmod'ed directories will be empty and return "." and ".." -- no harm.
And directories with tricky enough readdir and lookup shouldn't be modular.
We definitely don't want such modular code.

Removing ->owner will also make PDE smaller.

So, let's nuke it.

Kudos to Jeff Layton for reminding about this, let's say, oversight.

http://bugzilla.kernel.org/show_bug.cgi?id=12454

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>

11 files changed, 4 insertions, 30 deletions

diff --git a/net/appletalk/atalk_proc.c b/net/appletalk/atalk_proc.c
index 162199a2d74f..fd8e0847b254 100644
--- a/net/appletalk/atalk_proc.c
+++ b/net/appletalk/atalk_proc.c
@@ -281,7 +281,6 @@ int __init atalk_proc_init(void)
         atalk_proc_dir = proc_mkdir("atalk", init_net.proc_net);
         if (!atalk_proc_dir)
                 goto out;
-        atalk_proc_dir->owner = THIS_MODULE;
 
         p = proc_create("interface", S_IRUGO, atalk_proc_dir,
                         &atalk_seq_interface_fops);
diff --git a/net/atm/mpoa_proc.c b/net/atm/mpoa_proc.c
index 4990541ef5da..1a0f5ccea9c4 100644
--- a/net/atm/mpoa_proc.c
+++ b/net/atm/mpoa_proc.c
@@ -281,7 +281,6 @@ int mpc_proc_init(void)
                 printk(KERN_ERR "Unable to initialize /proc/atm/%s\n", STAT_FILE_NAME);
                 return -ENOMEM;
         }
-        p->owner = THIS_MODULE;
         return 0;
 }
 
diff --git a/net/atm/proc.c b/net/atm/proc.c
index 49487b313f22..e7b3b273907d 100644
--- a/net/atm/proc.c
+++ b/net/atm/proc.c
@@ -476,7 +476,6 @@ int __init atm_proc_init(void)
                                      atm_proc_root, e->proc_fops);
                 if (!dirent)
                         goto err_out_remove;
-                dirent->owner = THIS_MODULE;
                 e->dirent = dirent;
         }
         ret = 0;
diff --git a/net/can/bcm.c b/net/can/bcm.c
index b7c7d4651136..95d7f32643ae 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -1604,10 +1604,6 @@ static int __init bcm_module_init(void)
 
         /* create /proc/net/can-bcm directory */
         proc_dir = proc_mkdir("can-bcm", init_net.proc_net);
-
-        if (proc_dir)
-                proc_dir->owner = THIS_MODULE;
-
         return 0;
 }
 
diff --git a/net/can/proc.c b/net/can/proc.c
index 520fef5e5398..1463653dbe34 100644
--- a/net/can/proc.c
+++ b/net/can/proc.c
@@ -473,8 +473,6 @@ void can_init_proc(void)
                 return;
         }
 
-        can_dir->owner = THIS_MODULE;
-
         /* own procfs entries from the AF_CAN core */
         pde_version     = can_create_proc_readentry(CAN_PROC_VERSION, 0644,
                                         can_proc_read_version, NULL);
diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index 32d419f5ac98..3779c1438c11 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -3806,7 +3806,6 @@ static int __init pg_init(void)
         pg_proc_dir = proc_mkdir(PG_PROC_DIR, init_net.proc_net);
         if (!pg_proc_dir)
                 return -ENODEV;
-        pg_proc_dir->owner = THIS_MODULE;
 
         pe = proc_create(PGCTRL, 0600, pg_proc_dir, &pktgen_fops);
         if (pe == NULL) {
diff --git a/net/irda/irproc.c b/net/irda/irproc.c
index 88e80a312732..8ff1861649e8 100644
--- a/net/irda/irproc.c
+++ b/net/irda/irproc.c
@@ -70,7 +70,6 @@ void __init irda_proc_register(void)
         proc_irda = proc_mkdir("irda", init_net.proc_net);
         if (proc_irda == NULL)
                 return;
-        proc_irda->owner = THIS_MODULE;
 
         for (i = 0; i < ARRAY_SIZE(irda_dirs); i++)
                 d = proc_create(irda_dirs[i].name, 0, proc_irda,
diff --git a/net/llc/llc_proc.c b/net/llc/llc_proc.c
index b58bd7c6cdf8..d208b3396d94 100644
--- a/net/llc/llc_proc.c
+++ b/net/llc/llc_proc.c
@@ -236,7 +236,6 @@ int __init llc_proc_init(void)
         llc_proc_dir = proc_mkdir("llc", init_net.proc_net);
         if (!llc_proc_dir)
                 goto out;
-        llc_proc_dir->owner = THIS_MODULE;
 
         p = proc_create("socket", S_IRUGO, llc_proc_dir, &llc_seq_socket_fops);
         if (!p)
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index cb198af8887c..8eb3e61cb701 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -106,12 +106,8 @@ static __init int sctp_proc_init(void)
                 goto out_nomem;
 #ifdef CONFIG_PROC_FS
         if (!proc_net_sctp) {
-                struct proc_dir_entry *ent;
-                ent = proc_mkdir("sctp", init_net.proc_net);
-                if (ent) {
-                        ent->owner = THIS_MODULE;
-                        proc_net_sctp = ent;
-                } else
+                proc_net_sctp = proc_mkdir("sctp", init_net.proc_net);
+                if (!proc_net_sctp)
                         goto out_free_percpu;
         }
 
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 4735caad26ed..20029a79a5de 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -313,7 +313,6 @@ static int create_cache_proc_entries(struct cache_detail *cd)
         cd->proc_ent = proc_mkdir(cd->name, proc_net_rpc);
         if (cd->proc_ent == NULL)
                 goto out_nomem;
-        cd->proc_ent->owner = cd->owner;
         cd->channel_ent = cd->content_ent = NULL;
 
         p = proc_create_data("flush", S_IFREG|S_IRUSR|S_IWUSR,
@@ -321,7 +320,6 @@ static int create_cache_proc_entries(struct cache_detail *cd)
         cd->flush_ent = p;
         if (p == NULL)
                 goto out_nomem;
-        p->owner = cd->owner;
 
         if (cd->cache_request || cd->cache_parse) {
                 p = proc_create_data("channel", S_IFREG|S_IRUSR|S_IWUSR,
@@ -329,7 +327,6 @@ static int create_cache_proc_entries(struct cache_detail *cd)
                 cd->channel_ent = p;
                 if (p == NULL)
                         goto out_nomem;
-                p->owner = cd->owner;
         }
         if (cd->cache_show) {
                 p = proc_create_data("content", S_IFREG|S_IRUSR|S_IWUSR,
@@ -337,7 +334,6 @@ static int create_cache_proc_entries(struct cache_detail *cd)
                 cd->content_ent = p;
                 if (p == NULL)
                         goto out_nomem;
-                p->owner = cd->owner;
         }
         return 0;
 out_nomem:
diff --git a/net/sunrpc/stats.c b/net/sunrpc/stats.c
index 085372ef4feb..1ef6e46d9da2 100644
--- a/net/sunrpc/stats.c
+++ b/net/sunrpc/stats.c
@@ -262,14 +262,8 @@ void
 rpc_proc_init(void)
 {
         dprintk("RPC:       registering /proc/net/rpc\n");
-        if (!proc_net_rpc) {
-                struct proc_dir_entry *ent;
-                ent = proc_mkdir("rpc", init_net.proc_net);
-                if (ent) {
-                        ent->owner = THIS_MODULE;
-                        proc_net_rpc = ent;
-                }
-        }
+        if (!proc_net_rpc)
+                proc_net_rpc = proc_mkdir("rpc", init_net.proc_net);
 }
 
 void