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, 2 insertions, 8 deletions

diff --git a/drivers/rtc/rtc-proc.c b/drivers/rtc/rtc-proc.c
index 0c6257a034f..c086fc30a84 100644
--- a/drivers/rtc/rtc-proc.c
+++ b/drivers/rtc/rtc-proc.c
@@ -105,14 +105,8 @@ static const struct file_operations rtc_proc_fops = {
 
 void rtc_proc_add_device(struct rtc_device *rtc)
 {
-	if (rtc->id == 0) {
-		struct proc_dir_entry *ent;
-
-		ent = proc_create_data("driver/rtc", 0, NULL,
-				       &rtc_proc_fops, rtc);
-		if (ent)
-			ent->owner = rtc->owner;
-	}
+	if (rtc->id == 0)
+		proc_create_data("driver/rtc", 0, NULL, &rtc_proc_fops, rtc);
 }
 
 void rtc_proc_del_device(struct rtc_device *rtc)