FAILED: patch "[PATCH] dm cache metadata: ignore hints array being too small during" failed to apply to 3.18-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 3.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 4561ffca88c546f96367f94b8f1e4715a9c62314 Mon Sep 17 00:00:00 2001
From: Joe Thornber <ejt@redhat.com>
Date: Mon, 24 Sep 2018 16:19:30 -0400
Subject: [PATCH] dm cache metadata: ignore hints array being too small during
 resize

Commit fd2fa9541 ("dm cache metadata: save in-core policy_hint_size to
on-disk superblock") enabled previously written policy hints to be
used after a cache is reactivated.  But in doing so the cache
metadata's hint array was left exposed to out of bounds access because
on resize the metadata's on-disk hint array wasn't ever extended.

Fix this by ignoring that there are no on-disk hints associated with the
newly added cache blocks.  An expanded on-disk hint array is later
rewritten upon the next clean shutdown of the cache.

Fixes: fd2fa9541 ("dm cache metadata: save in-core policy_hint_size to on-disk superblock")
Cc: stable@vger.kernel.org
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-cache-metadata.c b/drivers/md/dm-cache-metadata.c
index 69dddeab124c..5936de71883f 100644
--- a/drivers/md/dm-cache-metadata.c
+++ b/drivers/md/dm-cache-metadata.c
@@ -1455,8 +1455,8 @@ static int __load_mappings(struct dm_cache_metadata *cmd,
 		if (hints_valid) {
 			r = dm_array_cursor_next(&cmd->hint_cursor);
 			if (r) {
-				DMERR("dm_array_cursor_next for hint failed");
-				goto out;
+				dm_array_cursor_end(&cmd->hint_cursor);
+				hints_valid = false;
 			}
 		}