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>

7 files changed, 3 insertions, 26 deletions

diff --git a/arch/alpha/kernel/srm_env.c b/arch/alpha/kernel/srm_env.c
index 78ad7cd..d12af47 100644
--- a/arch/alpha/kernel/srm_env.c
+++ b/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;
 	}
diff --git a/arch/blackfin/mm/sram-alloc.c b/arch/blackfin/mm/sram-alloc.c
index 834cab7..530d139 100644
--- a/arch/blackfin/mm/sram-alloc.c
+++ b/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;
 }
diff --git a/arch/ia64/kernel/palinfo.c b/arch/ia64/kernel/palinfo.c
index e5c57f4..a4f19c7 100644
--- a/arch/ia64/kernel/palinfo.c
+++ b/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++;
 	}
 }
diff --git a/arch/ia64/sn/kernel/sn2/prominfo_proc.c b/arch/ia64/sn/kernel/sn2/prominfo_proc.c
index 4dcce3d..e633288 100644
--- a/arch/ia64/sn/kernel/sn2/prominfo_proc.c
+++ b/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++;
 	}
 
diff --git a/arch/powerpc/kernel/rtas_flash.c b/arch/powerpc/kernel/rtas_flash.c
index 149cb11..13011a9 100644
--- a/arch/powerpc/kernel/rtas_flash.c
+++ b/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);
 	}
 }
diff --git a/arch/sparc/kernel/led.c b/arch/sparc/kernel/led.c
index adaaed4..00d034e 100644
--- a/arch/sparc/kernel/led.c
+++ b/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",
diff --git a/arch/x86/kernel/cpu/mtrr/if.c b/arch/x86/kernel/cpu/mtrr/if.c
index 4c42146..fb73a52 100644
--- a/arch/x86/kernel/cpu/mtrr/if.c
+++ b/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;
 }