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>

2 files changed, 0 insertions, 2 deletions

diff --git a/net/atm/mpoa_proc.c b/net/atm/mpoa_proc.c
index 4990541..1a0f5cc 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 49487b3..e7b3b273 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;