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, 3 deletions

diff --git a/drivers/acpi/button.c b/drivers/acpi/button.c
index 171fd91..c2f0606 100644
--- a/drivers/acpi/button.c
+++ b/drivers/acpi/button.c
@@ -200,12 +200,10 @@ static int acpi_button_add_fs(struct acpi_device *device)
 
 	if (!entry)
 		return -ENODEV;
-	entry->owner = THIS_MODULE;
 
 	acpi_device_dir(device) = proc_mkdir(acpi_device_bid(device), entry);
 	if (!acpi_device_dir(device))
 		return -ENODEV;
-	acpi_device_dir(device)->owner = THIS_MODULE;
 
 	/* 'info' [R] */
 	entry = proc_create_data(ACPI_BUTTON_FILE_INFO,
@@ -522,7 +520,6 @@ static int __init acpi_button_init(void)
 	acpi_button_dir = proc_mkdir(ACPI_BUTTON_CLASS, acpi_root_dir);
 	if (!acpi_button_dir)
 		return -ENODEV;
-	acpi_button_dir->owner = THIS_MODULE;
 	result = acpi_bus_register_driver(&acpi_button_driver);
 	if (result < 0) {
 		remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);