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>
diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index e11dc22..d78ade30 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -58,11 +58,8 @@
/* Let go of any associated proc directory entry */
de = PROC_I(inode)->pde;
- if (de) {
- if (de->owner)
- module_put(de->owner);
+ if (de)
de_put(de);
- }
if (PROC_I(inode)->sysctl)
sysctl_head_put(PROC_I(inode)->sysctl);
clear_inode(inode);
@@ -449,12 +446,9 @@
{
struct inode * inode;
- if (!try_module_get(de->owner))
- goto out_mod;
-
inode = iget_locked(sb, ino);
if (!inode)
- goto out_ino;
+ return NULL;
if (inode->i_state & I_NEW) {
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
PROC_I(inode)->fd = 0;
@@ -485,16 +479,9 @@
}
}
unlock_new_inode(inode);
- } else {
- module_put(de->owner);
+ } else
de_put(de);
- }
return inode;
-
-out_ino:
- module_put(de->owner);
-out_mod:
- return NULL;
}
int proc_fill_super(struct super_block *s)