[3.16.y-ckt stable] Patch "md/bitmap: return an error when bitmap superblock is corrupt." has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    md/bitmap: return an error when bitmap superblock is corrupt.

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt17.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From b1dd54850235ddbfd02a56f268c863c11cacd957 Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb at suse.com>
Date: Fri, 14 Aug 2015 17:04:21 +1000
Subject: md/bitmap: return an error when bitmap superblock is corrupt.

commit b97e92574c0bf335db1cd2ec491d8ff5cd5d0b49 upstream
    Use separate bitmaps for each nodes in the cluster

bitmap_read_sb() validates the bitmap superblock that it reads in.
If it finds an inconsistency like a bad magic number or out-of-range
version number, it prints an error and returns, but it incorrectly
returns zero, so the array is still assembled with the (invalid) bitmap.

This means it could try to use a bitmap with a new version number which
it therefore does not understand.

This bug was introduced in 3.5 and fix as part of a larger patch in 4.1.
So the patch is suitable for any -stable kernel in that range.

Fixes: 27581e5ae01f ("md/bitmap: centralise allocation of bitmap file pages.")
Signed-off-by: NeilBrown <neilb at suse.com>
Reported-by: GuoQing Jiang <gqjiang at suse.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/md/bitmap.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index da3604e73e8a..cced062cab4b 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -564,6 +564,8 @@ static int bitmap_read_sb(struct bitmap *bitmap)
 	if (err)
 		return err;

+	err = -EINVAL;
+
 	sb = kmap_atomic(sb_page);

 	chunksize = le32_to_cpu(sb->chunksize);