Patch "drivers/base/memory: fix an unlikely reference counting issue in __add_memory_block()" has been added to the 5.18-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    drivers/base/memory: fix an unlikely reference counting issue in __add_memory_block()

to the 5.18-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     drivers-base-memory-fix-an-unlikely-reference-counti.patch
and it can be found in the queue-5.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 934833c4c985505c13922c192b73315e8065d2cb
Author: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
Date:   Thu Apr 28 23:16:19 2022 -0700

    drivers/base/memory: fix an unlikely reference counting issue in __add_memory_block()
    
    [ 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>

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;
 }