FAILED: patch "[PATCH] btrfs: init csum_list before possible free" failed to apply to 4.4-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.4-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 e49be14b8d80e23bb7c53d78c21717a474ade76b Mon Sep 17 00:00:00 2001
From: Dan Robertson <dan@dlrobertson.com>
Date: Tue, 19 Feb 2019 02:56:43 +0000
Subject: [PATCH] btrfs: init csum_list before possible free

The scrub_ctx csum_list member must be initialized before scrub_free_ctx
is called. If the csum_list is not initialized beforehand, the
list_empty call in scrub_free_csums will result in a null deref if the
allocation fails in the for loop.

Fixes: a2de733c78fa ("btrfs: scrub")
CC: stable@vger.kernel.org # 3.0+
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Dan Robertson <dan@dlrobertson.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 669bedfec4a9..a99588536c79 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -584,6 +584,7 @@ static noinline_for_stack struct scrub_ctx *scrub_setup_ctx(
 	sctx->pages_per_rd_bio = SCRUB_PAGES_PER_RD_BIO;
 	sctx->curr = -1;
 	sctx->fs_info = fs_info;
+	INIT_LIST_HEAD(&sctx->csum_list);
 	for (i = 0; i < SCRUB_BIOS_PER_SCTX; ++i) {
 		struct scrub_bio *sbio;
 
@@ -608,7 +609,6 @@ static noinline_for_stack struct scrub_ctx *scrub_setup_ctx(
 	atomic_set(&sctx->workers_pending, 0);
 	atomic_set(&sctx->cancel_req, 0);
 	sctx->csum_size = btrfs_super_csum_size(fs_info->super_copy);
-	INIT_LIST_HEAD(&sctx->csum_list);
 
 	spin_lock_init(&sctx->list_lock);
 	spin_lock_init(&sctx->stat_lock);