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>

2 files changed, 2 insertions, 9 deletions

diff --git a/arch/ia64/kernel/palinfo.c b/arch/ia64/kernel/palinfo.c
index e5c57f413ca..a4f19c70aad 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 4dcce3d0e04..e6332881864 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++;
 	}