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>

Documentation/DocBook/procfs_example.c

@@ -117,9 +117,6 @@ static int __init init_procfs_example(void)
 		rv = -ENOMEM;
 		goto out;
 	}
-	
-	example_dir->owner = THIS_MODULE;
-	
 	/* create jiffies using convenience function */
 	jiffies_file = create_proc_read_entry("jiffies", 
 					      0444, example_dir, 
@@ -130,8 +127,6 @@ static int __init init_procfs_example(void)
 		goto no_jiffies;
 	}
 
-	jiffies_file->owner = THIS_MODULE;
-
 	/* create foo and bar files using same callback
 	 * functions 
 	 */
@@ -146,7 +141,6 @@ static int __init init_procfs_example(void)
 	foo_file->data = &foo_data;
 	foo_file->read_proc = proc_read_foobar;
 	foo_file->write_proc = proc_write_foobar;
-	foo_file->owner = THIS_MODULE;
 		
 	bar_file = create_proc_entry("bar", 0644, example_dir);
 	if(bar_file == NULL) {
@@ -159,7 +153,6 @@ static int __init init_procfs_example(void)
 	bar_file->data = &bar_data;
 	bar_file->read_proc = proc_read_foobar;
 	bar_file->write_proc = proc_write_foobar;
-	bar_file->owner = THIS_MODULE;
 		
 	/* create symlink */
 	symlink = proc_symlink("jiffies_too", example_dir, 
@@ -169,8 +162,6 @@ static int __init init_procfs_example(void)
 		goto no_symlink;
 	}
 
-	symlink->owner = THIS_MODULE;
-
 	/* everything OK */
 	printk(KERN_INFO "%s %s initialised\n",
 	       MODULE_NAME, MODULE_VERS);

arch/alpha/kernel/srm_env.c

@@ -218,7 +218,6 @@ srm_env_init(void)
 				BASE_DIR);
 		goto cleanup;
 	}
-	base_dir->owner = THIS_MODULE;
 
 	/*
 	 * Create per-name subdirectory
@@ -229,7 +228,6 @@ srm_env_init(void)
 				BASE_DIR, NAMED_DIR);
 		goto cleanup;
 	}
-	named_dir->owner = THIS_MODULE;
 
 	/*
 	 * Create per-number subdirectory
@@ -241,7 +239,6 @@ srm_env_init(void)
 		goto cleanup;
 
 	}
-	numbered_dir->owner = THIS_MODULE;
 
 	/*
 	 * Create all named nodes
@@ -254,7 +251,6 @@ srm_env_init(void)
 			goto cleanup;
 
 		entry->proc_entry->data		= (void *) entry;
-		entry->proc_entry->owner	= THIS_MODULE;
 		entry->proc_entry->read_proc	= srm_env_read;
 		entry->proc_entry->write_proc	= srm_env_write;
 
@@ -275,7 +271,6 @@ srm_env_init(void)
 
 		entry->id			= var_num;
 		entry->proc_entry->data		= (void *) entry;
-		entry->proc_entry->owner	= THIS_MODULE;
 		entry->proc_entry->read_proc	= srm_env_read;
 		entry->proc_entry->write_proc	= srm_env_write;
 	}

arch/blackfin/mm/sram-alloc.c

@@ -854,7 +854,6 @@ static int __init sram_proc_init(void)
 		printk(KERN_WARNING "unable to create /proc/sram\n");
 		return -1;
 	}
-	ptr->owner = THIS_MODULE;
 	ptr->read_proc = sram_proc_read;
 	return 0;
 }

arch/ia64/kernel/palinfo.c

@@ -1002,8 +1002,6 @@ create_palinfo_proc_entries(unsigned int cpu)
 		*pdir = create_proc_read_entry(
 				palinfo_entries[j].name, 0, cpu_dir,
 				palinfo_read_entry, (void *)f.value);
-		if (*pdir)
-			(*pdir)->owner = THIS_MODULE;
 		pdir++;
 	}
 }

arch/ia64/sn/kernel/sn2/prominfo_proc.c

@@ -225,7 +225,6 @@ static struct proc_dir_entry *sgi_prominfo_entry;
 int __init prominfo_init(void)
 {
 	struct proc_dir_entry **entp;
-	struct proc_dir_entry *p;
 	cnodeid_t cnodeid;
 	unsigned long nasid;
 	int size;
@@ -246,14 +245,10 @@ int __init prominfo_init(void)
 		sprintf(name, "node%d", cnodeid);
 		*entp = proc_mkdir(name, sgi_prominfo_entry);
 		nasid = cnodeid_to_nasid(cnodeid);
-		p = create_proc_read_entry("fit", 0, *entp, read_fit_entry,
+		create_proc_read_entry("fit", 0, *entp, read_fit_entry,
 					   (void *)nasid);
-		if (p)
-			p->owner = THIS_MODULE;
-		p = create_proc_read_entry("version", 0, *entp,
+		create_proc_read_entry("version", 0, *entp,
 					   read_version_entry, (void *)nasid);
-		if (p)
-			p->owner = THIS_MODULE;
 		entp++;
 	}
 

arch/powerpc/kernel/rtas_flash.c

@@ -669,7 +669,6 @@ static void remove_flash_pde(struct proc_dir_entry *dp)
 {
 	if (dp) {
 		kfree(dp->data);
-		dp->owner = NULL;
 		remove_proc_entry(dp->name, dp->parent);
 	}
 }

arch/sparc/kernel/led.c

@@ -126,7 +126,6 @@ static int __init led_init(void)
 	led = proc_create("led", 0, NULL, &led_proc_fops);
 	if (!led)
 		return -ENOMEM;
-	led->owner = THIS_MODULE;
 
 	printk(KERN_INFO
 	       "led: version %s, Lars Kotthoff <metalhead@metalhead.ws>\n",

arch/x86/kernel/cpu/mtrr/if.c

@@ -377,10 +377,6 @@ static const struct file_operations mtrr_fops = {
 	.release = mtrr_close,
 };
 
-
-static struct proc_dir_entry *proc_root_mtrr;
-
-
 static int mtrr_seq_show(struct seq_file *seq, void *offset)
 {
 	char factor;
@@ -423,11 +419,7 @@ static int __init mtrr_if_init(void)
 	    (!cpu_has(c, X86_FEATURE_CENTAUR_MCR)))
 		return -ENODEV;
 
-	proc_root_mtrr =
-		proc_create("mtrr", S_IWUSR | S_IRUGO, NULL, &mtrr_fops);
-
-	if (proc_root_mtrr)
-		proc_root_mtrr->owner = THIS_MODULE;
+	proc_create("mtrr", S_IWUSR | S_IRUGO, NULL, &mtrr_fops);
 	return 0;
 }
 

drivers/acpi/ac.c

@@ -191,7 +191,6 @@ static int acpi_ac_add_fs(struct acpi_device *device)
 						     acpi_ac_dir);
 		if (!acpi_device_dir(device))
 			return -ENODEV;
-		acpi_device_dir(device)->owner = THIS_MODULE;
 	}
 
 	/* 'state' [R] */

drivers/acpi/battery.c

@@ -760,7 +760,6 @@ static int acpi_battery_add_fs(struct acpi_device *device)
 						     acpi_battery_dir);
 		if (!acpi_device_dir(device))
 			return -ENODEV;
-		acpi_device_dir(device)->owner = THIS_MODULE;
 	}
 
 	for (i = 0; i < ACPI_BATTERY_NUMFILES; ++i) {

drivers/acpi/button.c

@@ -200,12 +200,10 @@ static int acpi_button_add_fs(struct acpi_device *device)
 
 	if (!entry)
 		return -ENODEV;
-	entry->owner = THIS_MODULE;
 
 	acpi_device_dir(device) = proc_mkdir(acpi_device_bid(device), entry);
 	if (!acpi_device_dir(device))
 		return -ENODEV;
-	acpi_device_dir(device)->owner = THIS_MODULE;
 
 	/* 'info' [R] */
 	entry = proc_create_data(ACPI_BUTTON_FILE_INFO,
@@ -522,7 +520,6 @@ static int __init acpi_button_init(void)
 	acpi_button_dir = proc_mkdir(ACPI_BUTTON_CLASS, acpi_root_dir);
 	if (!acpi_button_dir)
 		return -ENODEV;
-	acpi_button_dir->owner = THIS_MODULE;
 	result = acpi_bus_register_driver(&acpi_button_driver);
 	if (result < 0) {
 		remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);

drivers/acpi/fan.c

@@ -193,7 +193,6 @@ static int acpi_fan_add_fs(struct acpi_device *device)
 						     acpi_fan_dir);
 		if (!acpi_device_dir(device))
 			return -ENODEV;
-		acpi_device_dir(device)->owner = THIS_MODULE;
 	}
 
 	/* 'status' [R/W] */
@@ -347,7 +346,6 @@ static int __init acpi_fan_init(void)
 	acpi_fan_dir = proc_mkdir(ACPI_FAN_CLASS, acpi_root_dir);
 	if (!acpi_fan_dir)
 		return -ENODEV;
-	acpi_fan_dir->owner = THIS_MODULE;
 #endif
 
 	result = acpi_bus_register_driver(&acpi_fan_driver);

drivers/acpi/processor_core.c

@@ -359,7 +359,6 @@ static int acpi_processor_add_fs(struct acpi_device *device)
 		if (!acpi_device_dir(device))
 			return -ENODEV;
 	}
-	acpi_device_dir(device)->owner = THIS_MODULE;
 
 	/* 'info' [R] */
 	entry = proc_create_data(ACPI_PROCESSOR_FILE_INFO,
@@ -1137,7 +1136,6 @@ static int __init acpi_processor_init(void)
 	acpi_processor_dir = proc_mkdir(ACPI_PROCESSOR_CLASS, acpi_root_dir);
 	if (!acpi_processor_dir)
 		return -ENOMEM;
-	acpi_processor_dir->owner = THIS_MODULE;
 
 	/*
 	 * Check whether the system is DMI table. If yes, OSPM

drivers/acpi/sbs.c

@@ -488,7 +488,6 @@ acpi_sbs_add_fs(struct proc_dir_entry **dir,
 		if (!*dir) {
 			return -ENODEV;
 		}
-		(*dir)->owner = THIS_MODULE;
 	}
 
 	/* 'info' [R] */

drivers/acpi/thermal.c

@@ -1506,7 +1506,6 @@ static int acpi_thermal_add_fs(struct acpi_device *device)
 						     acpi_thermal_dir);
 		if (!acpi_device_dir(device))
 			return -ENODEV;
-		acpi_device_dir(device)->owner = THIS_MODULE;
 	}
 
 	/* 'state' [R] */
@@ -1875,7 +1874,6 @@ static int __init acpi_thermal_init(void)
 	acpi_thermal_dir = proc_mkdir(ACPI_THERMAL_CLASS, acpi_root_dir);
 	if (!acpi_thermal_dir)
 		return -ENODEV;
-	acpi_thermal_dir->owner = THIS_MODULE;
 
 	result = acpi_bus_register_driver(&acpi_thermal_driver);
 	if (result < 0) {

drivers/acpi/video.c

@@ -1125,8 +1125,6 @@ static int acpi_video_device_add_fs(struct acpi_device *device)
 	if (!device_dir)
 		return -ENOMEM;
 
-	device_dir->owner = THIS_MODULE;
-
 	/* 'info' [R] */
 	entry = proc_create_data("info", S_IRUGO, device_dir,
 			&acpi_video_device_info_fops, acpi_driver_data(device));
@@ -1403,8 +1401,6 @@ static int acpi_video_bus_add_fs(struct acpi_device *device)
 	if (!device_dir)
 		return -ENOMEM;
 
-	device_dir->owner = THIS_MODULE;
-
 	/* 'info' [R] */
 	entry = proc_create_data("info", S_IRUGO, device_dir,
 				 &acpi_video_bus_info_fops,
@@ -2131,7 +2127,6 @@ static int __init acpi_video_init(void)
 	acpi_video_dir = proc_mkdir(ACPI_VIDEO_CLASS, acpi_root_dir);
 	if (!acpi_video_dir)
 		return -ENODEV;
-	acpi_video_dir->owner = THIS_MODULE;
 
 	result = acpi_bus_register_driver(&acpi_video_bus);
 	if (result < 0) {

drivers/block/ps3vram.c

@@ -551,8 +551,6 @@ static void __devinit ps3vram_proc_init(struct ps3_system_bus_device *dev)
 		dev_warn(&dev->core, "failed to create /proc entry\n");
 		return;
 	}
-
-	pde->owner = THIS_MODULE;
 	pde->data = priv;
 }
 

drivers/char/ipmi/ipmi_msghandler.c

@@ -1944,7 +1944,7 @@ static int stat_file_read_proc(char *page, char **start, off_t off,
 
 int ipmi_smi_add_proc_entry(ipmi_smi_t smi, char *name,
 			    read_proc_t *read_proc,
-			    void *data, struct module *owner)
+			    void *data)
 {
 	int                    rv = 0;
 #ifdef CONFIG_PROC_FS
@@ -1970,7 +1970,6 @@ int ipmi_smi_add_proc_entry(ipmi_smi_t smi, char *name,
 	} else {
 		file->data = data;
 		file->read_proc = read_proc;
-		file->owner = owner;
 
 		mutex_lock(&smi->proc_entry_lock);
 		/* Stick it on the list. */
@@ -1993,23 +1992,21 @@ static int add_proc_entries(ipmi_smi_t smi, int num)
 	smi->proc_dir = proc_mkdir(smi->proc_dir_name, proc_ipmi_root);
 	if (!smi->proc_dir)
 		rv = -ENOMEM;
-	else
-		smi->proc_dir->owner = THIS_MODULE;
 
 	if (rv == 0)
 		rv = ipmi_smi_add_proc_entry(smi, "stats",
 					     stat_file_read_proc,
-					     smi, THIS_MODULE);
+					     smi);
 
 	if (rv == 0)
 		rv = ipmi_smi_add_proc_entry(smi, "ipmb",
 					     ipmb_file_read_proc,
-					     smi, THIS_MODULE);
+					     smi);
 
 	if (rv == 0)
 		rv = ipmi_smi_add_proc_entry(smi, "version",
 					     version_file_read_proc,
-					     smi, THIS_MODULE);
+					     smi);
 #endif /* CONFIG_PROC_FS */
 
 	return rv;
@@ -4265,7 +4262,6 @@ static int ipmi_init_msghandler(void)
 	    return -ENOMEM;
 	}
 
-	proc_ipmi_root->owner = THIS_MODULE;
 #endif /* CONFIG_PROC_FS */
 
 	setup_timer(&ipmi_timer, ipmi_timeout, 0);

drivers/char/ipmi/ipmi_si_intf.c

@@ -2899,7 +2899,7 @@ static int try_smi_init(struct smi_info *new_smi)
 
 	rv = ipmi_smi_add_proc_entry(new_smi->intf, "type",
 				     type_file_read_proc,
-				     new_smi, THIS_MODULE);
+				     new_smi);
 	if (rv) {
 		printk(KERN_ERR
 		       "ipmi_si: Unable to create proc entry: %d\n",
@@ -2909,7 +2909,7 @@ static int try_smi_init(struct smi_info *new_smi)
 
 	rv = ipmi_smi_add_proc_entry(new_smi->intf, "si_stats",
 				     stat_file_read_proc,
-				     new_smi, THIS_MODULE);
+				     new_smi);
 	if (rv) {
 		printk(KERN_ERR
 		       "ipmi_si: Unable to create proc entry: %d\n",
@@ -2919,7 +2919,7 @@ static int try_smi_init(struct smi_info *new_smi)
 
 	rv = ipmi_smi_add_proc_entry(new_smi->intf, "params",
 				     param_read_proc,
-				     new_smi, THIS_MODULE);
+				     new_smi);
 	if (rv) {
 		printk(KERN_ERR
 		       "ipmi_si: Unable to create proc entry: %d\n",

drivers/input/input.c

@@ -903,8 +903,6 @@ static int __init input_proc_init(void)
 	if (!proc_bus_input_dir)
 		return -ENOMEM;
 
-	proc_bus_input_dir->owner = THIS_MODULE;
-
 	entry = proc_create("devices", 0, proc_bus_input_dir,
 			    &input_devices_fileops);
 	if (!entry)