FAILED: patch "[PATCH] bcache: Fix __bch_btree_node_alloc to make the failure" failed to apply to 4.19-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.19-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>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y
git checkout FETCH_HEAD
git cherry-pick -x 80fca8a10b604afad6c14213fdfd816c4eda3ee4
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2023071621-lubricate-dragging-07c6@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^..

Possible dependencies:

80fca8a10b60 ("bcache: Fix __bch_btree_node_alloc to make the failure behavior consistent")
17e4aed8309f ("bcache: remove 'int n' from parameter list of bch_bucket_alloc_set()")
8792099f9ad4 ("bcache: use MAX_CACHES_PER_SET instead of magic number 8 in __bch_bucket_alloc_set")

thanks,

greg k-h

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

From 80fca8a10b604afad6c14213fdfd816c4eda3ee4 Mon Sep 17 00:00:00 2001
From: Zheng Wang <zyytlz.wz@163.com>
Date: Thu, 15 Jun 2023 20:12:22 +0800
Subject: [PATCH] bcache: Fix __bch_btree_node_alloc to make the failure
 behavior consistent

In some specific situations, the return value of __bch_btree_node_alloc
may be NULL. This may lead to a potential NULL pointer dereference in
caller function like a calling chain :
btree_split->bch_btree_node_alloc->__bch_btree_node_alloc.

Fix it by initializing the return value in __bch_btree_node_alloc.

Fixes: cafe56359144 ("bcache: A block layer cache")
Cc: stable@vger.kernel.org
Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
Signed-off-by: Coly Li <colyli@suse.de>
Link: https://lore.kernel.org/r/20230615121223.22502-6-colyli@suse.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 7c21e54468bf..0ddf91204782 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -1090,10 +1090,12 @@ struct btree *__bch_btree_node_alloc(struct cache_set *c, struct btree_op *op,
 				     struct btree *parent)
 {
 	BKEY_PADDED(key) k;
-	struct btree *b = ERR_PTR(-EAGAIN);
+	struct btree *b;
 
 	mutex_lock(&c->bucket_lock);
 retry:
+	/* return ERR_PTR(-EAGAIN) when it fails */
+	b = ERR_PTR(-EAGAIN);
 	if (__bch_bucket_alloc_set(c, RESERVE_BTREE, &k.key, wait))
 		goto err;