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>

1 files changed, 0 insertions, 4 deletions

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 4735caa..20029a7 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: