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 78ad7cd1bbd6..d12af472e1c0 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 834cab7438a8..530d1393a232 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 e5c57f413ca2..a4f19c70aadd 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 4dcce3d0e04c..e63328818643 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 149cb112cd1a..13011a96a977 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 adaaed4ea2fb..00d034ea2164 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 4c4214690dd1..fb73a52913a4 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;
 }