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, 7 deletions

diff --git a/drivers/net/irda/vlsi_ir.c b/drivers/net/irda/vlsi_ir.c
index 1243bc8e003..ac0e4b6b6b6 100644
--- a/drivers/net/irda/vlsi_ir.c
+++ b/drivers/net/irda/vlsi_ir.c
@@ -1871,13 +1871,6 @@ static int __init vlsi_mod_init(void)
          * without procfs - it's not required for the driver to work.
          */
         vlsi_proc_root = proc_mkdir(PROC_DIR, NULL);
-        if (vlsi_proc_root) {
-                /* protect registered procdir against module removal.
-                 * Because we are in the module init path there's no race
-                 * window after create_proc_entry (and no barrier needed).
-                 */
-                vlsi_proc_root->owner = THIS_MODULE;
-        }
 
         ret = pci_register_driver(&vlsi_irda_driver);