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/video/via/viafbdev.c b/drivers/video/via/viafbdev.c
index 37b433a..e327b848 100644
--- a/drivers/video/via/viafbdev.c
+++ b/drivers/video/via/viafbdev.c
@@ -2059,25 +2059,21 @@ static void viafb_init_proc(struct proc_dir_entry **viafb_entry)
 	if (viafb_entry) {
 		entry = create_proc_entry("dvp0", 0, *viafb_entry);
 		if (entry) {
-			entry->owner = THIS_MODULE;
 			entry->read_proc = viafb_dvp0_proc_read;
 			entry->write_proc = viafb_dvp0_proc_write;
 		}
 		entry = create_proc_entry("dvp1", 0, *viafb_entry);
 		if (entry) {
-			entry->owner = THIS_MODULE;
 			entry->read_proc = viafb_dvp1_proc_read;
 			entry->write_proc = viafb_dvp1_proc_write;
 		}
 		entry = create_proc_entry("dfph", 0, *viafb_entry);
 		if (entry) {
-			entry->owner = THIS_MODULE;
 			entry->read_proc = viafb_dfph_proc_read;
 			entry->write_proc = viafb_dfph_proc_write;
 		}
 		entry = create_proc_entry("dfpl", 0, *viafb_entry);
 		if (entry) {
-			entry->owner = THIS_MODULE;
 			entry->read_proc = viafb_dfpl_proc_read;
 			entry->write_proc = viafb_dfpl_proc_write;
 		}
@@ -2086,7 +2082,6 @@ static void viafb_init_proc(struct proc_dir_entry **viafb_entry)
 		    viaparinfo->chip_info->lvds_chip_info2.lvds_chip_name) {
 			entry = create_proc_entry("vt1636", 0, *viafb_entry);
 			if (entry) {
-				entry->owner = THIS_MODULE;
 				entry->read_proc = viafb_vt1636_proc_read;
 				entry->write_proc = viafb_vt1636_proc_write;
 			}