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 d63f26e..ba1f749 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 d243320..3dad27a3 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 40e60fc..9f18726 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();