[PATCH 5.10 293/452] drivers/base/memory: fix an unlikely reference counting issue in __add_memory_block()

[Greg Kroah-Hartman]

From: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>

[ Upstream commit f47f758cff59c68015d6b9b9c077110df7c2c828 ]

__add_memory_block() calls both put_device() and device_unregister() when
storing the memory block into the xarray.  This is incorrect because
xarray doesn't take an additional reference and device_unregister()
already calls put_device().

Triggering the issue looks really unlikely and its only effect should be
to log a spurious warning about a ref counted issue.

Link: https://lkml.kernel.org/r/d44c63d78affe844f020dc02ad6af29abc448fc4.1650611702.git.christophe.jaillet@xxxxxxxxxx
Fixes: 4fb6eabf1037 ("drivers/base/memory.c: cache memory blocks in xarray to accelerate lookup")
Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
Cc: Scott Cheloha <cheloha@xxxxxxxxxxxxxxxxxx>
Cc: Nathan Lynch <nathanl@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 de058d15b33e..49eb14271f28 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -560,10 +560,9 @@ int register_memory(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;
 }
 
-- 
2.35.1