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

BugLink: https://bugs.launchpad.net/bugs/1981864
[ 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@wanadoo.fr
Fixes: 4fb6eabf1037 ("drivers/base/memory.c: cache memory blocks in xarray to accelerate lookup")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Scott Cheloha <cheloha@linux.vnet.ibm.com>
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 60c38f9cf1a7538d525d9eb25607758bf394deb4..c0d501a3a7140068cf02d5332e4b088e8aa6a248 100644 (file)
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -634,10 +634,9 @@ 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;
 }