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>

3 files changed, 0 insertions, 8 deletions

diff --git a/drivers/platform/x86/asus_acpi.c b/drivers/platform/x86/asus_acpi.c
index d63f26e666a4..ba1f7497e4b9 100644
--- a/drivers/platform/x86/asus_acpi.c
+++ b/drivers/platform/x86/asus_acpi.c
@@ -987,7 +987,6 @@ asus_proc_add(char *name, proc_writefunc *writefunc,
         proc->write_proc = writefunc;
         proc->read_proc = readfunc;
         proc->data = acpi_driver_data(device);
-        proc->owner = THIS_MODULE;
         proc->uid = asus_uid;
         proc->gid = asus_gid;
         return 0;
@@ -1020,7 +1019,6 @@ static int asus_hotk_add_fs(struct acpi_device *device)
         if (proc) {
                 proc->read_proc = proc_read_info;
                 proc->data = acpi_driver_data(device);
-                proc->owner = THIS_MODULE;
                 proc->uid = asus_uid;
                 proc->gid = asus_gid;
         } else {
@@ -1436,7 +1434,6 @@ static int __init asus_acpi_init(void)
                 printk(KERN_ERR "Asus ACPI: Unable to create /proc entry\n");
                 return -ENODEV;
         }
-        asus_proc_dir->owner = THIS_MODULE;
 
         result = acpi_bus_register_driver(&asus_hotk_driver);
         if (result < 0) {
diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
index d2433204a40c..3dad27a385d3 100644
--- a/drivers/platform/x86/thinkpad_acpi.c
+++ b/drivers/platform/x86/thinkpad_acpi.c
@@ -6992,7 +6992,6 @@ static int __init ibm_init(struct ibm_init_struct *iibm)
                         ret = -ENODEV;
                         goto err_out;
                 }
-                entry->owner = THIS_MODULE;
                 entry->data = ibm;
                 entry->read_proc = &dispatch_procfs_read;
                 if (ibm->write)
@@ -7405,7 +7404,6 @@ static int __init thinkpad_acpi_module_init(void)
                 thinkpad_acpi_module_exit();
                 return -ENODEV;
         }
-        proc_dir->owner = THIS_MODULE;
 
         ret = platform_driver_register(&tpacpi_pdriver);
         if (ret) {
diff --git a/drivers/platform/x86/toshiba_acpi.c b/drivers/platform/x86/toshiba_acpi.c
index 40e60fc2e596..9f187265db8e 100644
--- a/drivers/platform/x86/toshiba_acpi.c
+++ b/drivers/platform/x86/toshiba_acpi.c
@@ -679,8 +679,6 @@ static acpi_status __init add_device(void)
                                               toshiba_proc_dir,
                                               (read_proc_t *) dispatch_read,
                                               item);
-                if (proc)
-                        proc->owner = THIS_MODULE;
                 if (proc && item->write_func)
                         proc->write_proc = (write_proc_t *) dispatch_write;
         }
@@ -772,7 +770,6 @@ static int __init toshiba_acpi_init(void)
                 toshiba_acpi_exit();
                 return -ENODEV;
         } else {
-                toshiba_proc_dir->owner = THIS_MODULE;
                 status = add_device();
                 if (ACPI_FAILURE(status)) {
                         toshiba_acpi_exit();