proc 1/2: do PDE usecounting even for ->read_proc, ->write_proc

struct proc_dir_entry::owner is going to be removed. Now it's only necessary
to protect PDEs which are using ->read_proc, ->write_proc hooks.

However, ->owner assignments are racy and make it very easy for someone to switch
->owner on live PDE (as some subsystems do) without fixing refcounts and so on.

http://bugzilla.kernel.org/show_bug.cgi?id=12454

So, ->owner is on death row.

Proxy file operations exist already (proc_file_operations), just bump usecount
when necessary.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index cd53ff838498..f6db9618a888 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -91,3 +91,4 @@ struct pde_opener {
         int (*release)(struct inode *, struct file *);
         struct list_head lh;
 };
+void pde_users_dec(struct proc_dir_entry *pde);