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
Git-commit: 80fca8a10b604afad6c14213fdfd816c4eda3ee4
Patch-mainline: v6.5-rc1
References: git-fixes

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.

(Coly Li: rebased for Linux 4.12 based SUSE kernel)

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>

---
 drivers/md/bcache/btree.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -1137,10 +1137,12 @@ struct btree *__bch_btree_node_alloc(str
 				     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, 1, wait))
 		goto err;