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, 1 insertions, 3 deletions

diff --git a/drivers/media/video/cpia.c b/drivers/media/video/cpia.c
index c3b0c8c63c7..43ab0adf3b6 100644
--- a/drivers/media/video/cpia.c
+++ b/drivers/media/video/cpia.c
@@ -1381,9 +1381,7 @@ static void proc_cpia_create(void)
 {
 	cpia_proc_root = proc_mkdir("cpia", NULL);
 
-	if (cpia_proc_root)
-		cpia_proc_root->owner = THIS_MODULE;
-	else
+	if (!cpia_proc_root)
 		LOG("Unable to initialise /proc/cpia\n");
 }