Patch "f2fs: set ->owner for debugfs status file's file_operations" has been added to the 4.4-stable tree

Patch "f2fs: set ->owner for debugfs status file's file_operations" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    f2fs: set ->owner for debugfs status file's file_operations

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     f2fs-set-owner-for-debugfs-status-file-s-file_operations.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 05e6ea2685c964db1e675a24a4f4e2adc22d2388 Mon Sep 17 00:00:00 2001
From: Nicolai Stange <nicstange@gmail.com>
Date: Sun, 20 Nov 2016 19:57:23 +0100
Subject: f2fs: set ->owner for debugfs status file's file_operations

From: Nicolai Stange <nicstange@gmail.com>

commit 05e6ea2685c964db1e675a24a4f4e2adc22d2388 upstream.

The struct file_operations instance serving the f2fs/status debugfs file
lacks an initialization of its ->owner.

This means that although that file might have been opened, the f2fs module
can still get removed. Any further operation on that opened file, releasing
included,  will cause accesses to unmapped memory.

Indeed, Mike Marshall reported the following:

  BUG: unable to handle kernel paging request at ffffffffa0307430
  IP: [<ffffffff8132a224>] full_proxy_release+0x24/0x90
  <...>
  Call Trace:
   [] __fput+0xdf/0x1d0
   [] ____fput+0xe/0x10
   [] task_work_run+0x8e/0xc0
   [] do_exit+0x2ae/0xae0
   [] ? __audit_syscall_entry+0xae/0x100
   [] ? syscall_trace_enter+0x1ca/0x310
   [] do_group_exit+0x44/0xc0
   [] SyS_exit_group+0x14/0x20
   [] do_syscall_64+0x61/0x150
   [] entry_SYSCALL64_slow_path+0x25/0x25
  <...>
  ---[ end trace f22ae883fa3ea6b8 ]---
  Fixing recursive fault but reboot is needed!

Fix this by initializing the f2fs/status file_operations' ->owner with
THIS_MODULE.

This will allow debugfs to grab a reference to the f2fs module upon any
open on that file, thus preventing it from getting removed.

Fixes: 902829aa0b72 ("f2fs: move proc files to debugfs")
Reported-by: Mike Marshall <hubcap@omnibond.com>
Reported-by: Martin Brandenburg <martin@omnibond.com>
Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/f2fs/debug.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/f2fs/debug.c
+++ b/fs/f2fs/debug.c
@@ -352,6 +352,7 @@ static int stat_open(struct inode *inode
 }
 
 static const struct file_operations stat_fops = {
+	.owner = THIS_MODULE,
 	.open = stat_open,
 	.read = seq_read,
 	.llseek = seq_lseek,


Patches currently in stable-queue which might be from nicstange@gmail.com are

queue-4.4/f2fs-set-owner-for-debugfs-status-file-s-file_operations.patch