linux-kernel - [PATCH] drivers/base/memory: Fix a reference counting issue in __add_memory

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Message-Id: <d44c63d78aafe844f920dc02ad6af25acc448fcf.1650611702.git.christophe.jaillet@wanadoo.fr>
Date:   Fri, 22 Apr 2022 09:15:21 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Scott Cheloha <cheloha@...ux.vnet.ibm.com>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nathan Lynch <nathanl@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: [PATCH] drivers/base/memory: Fix a reference counting issue in __add_memory_block()

There is no point in doing put_device()/device_unregister() on a
device that has just been registered a few lines above. This will lead to
a double reference decrement.

I guess that this put_device()/device_unregister() is a cut'n'paste from
remove_memory_block() (i.e. unregister_memory() at the time being) which
does need it.

Fixes: 4fb6eabf1037 ("drivers/base/memory.c: cache memory blocks in xarray to accelerate lookup")
Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
 drivers/base/memory.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 7222ff9b5e05..084d67fd55cc 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -636,10 +636,9 @@ static int __add_memory_block(struct memory_block *memory)
 	}
 	ret = xa_err(xa_store(&memory_blocks, memory->dev.id, memory,
 			      GFP_KERNEL));
-	if (ret) {
-		put_device(&memory->dev);
+	if (ret)
 		device_unregister(&memory->dev);
-	}
+
 	return ret;
 }
 
-- 
2.32.0