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; } }