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, 2 deletions

diff --git a/drivers/s390/block/dasd_proc.c b/drivers/s390/block/dasd_proc.c
index 2080ba6a69b0..654daa3cdfda 100644
--- a/drivers/s390/block/dasd_proc.c
+++ b/drivers/s390/block/dasd_proc.c
@@ -320,7 +320,6 @@ dasd_proc_init(void)
 	dasd_proc_root_entry = proc_mkdir("dasd", NULL);
 	if (!dasd_proc_root_entry)
 		goto out_nodasd;
-	dasd_proc_root_entry->owner = THIS_MODULE;
 	dasd_devices_entry = proc_create("devices",
 					 S_IFREG | S_IRUGO | S_IWUSR,
 					 dasd_proc_root_entry,
@@ -334,7 +333,6 @@ dasd_proc_init(void)
 		goto out_nostatistics;
 	dasd_statistics_entry->read_proc = dasd_statistics_read;
 	dasd_statistics_entry->write_proc = dasd_statistics_write;
-	dasd_statistics_entry->owner = THIS_MODULE;
 	return 0;
 
  out_nostatistics: