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, 5 deletions

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index bb5ed059114a..67cc36dc9b82 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -1125,8 +1125,6 @@ static int acpi_video_device_add_fs(struct acpi_device *device)
         if (!device_dir)
                 return -ENOMEM;
 
-        device_dir->owner = THIS_MODULE;
-
         /* 'info' [R] */
         entry = proc_create_data("info", S_IRUGO, device_dir,
                         &acpi_video_device_info_fops, acpi_driver_data(device));
@@ -1403,8 +1401,6 @@ static int acpi_video_bus_add_fs(struct acpi_device *device)
         if (!device_dir)
                 return -ENOMEM;
 
-        device_dir->owner = THIS_MODULE;
-
         /* 'info' [R] */
         entry = proc_create_data("info", S_IRUGO, device_dir,
                                  &acpi_video_bus_info_fops,
@@ -2131,7 +2127,6 @@ static int __init acpi_video_init(void)
         acpi_video_dir = proc_mkdir(ACPI_VIDEO_CLASS, acpi_root_dir);
         if (!acpi_video_dir)
                 return -ENODEV;
-        acpi_video_dir->owner = THIS_MODULE;
 
         result = acpi_bus_register_driver(&acpi_video_bus);
         if (result < 0) {