drivers/base/memory: set mem->altmap after successful device registration

If __add_memory_block() fails at xa_store() (under memory pressure for
example), device_unregister() is called, which eventually triggers
memory_block_release() with mem->altmap still set, causing a
WARN_ON(mem->altmap).  This was triggered by modifying virtio-mem driver.

Fix this by delaying the assignment of mem->altmap until after
__add_memory_block() has succeeded.

Link: https://lore.kernel.org/20260514092657.3057141-1-georgi.djakov@oss.qualcomm.com
Fixes: 1a8c64e11043 ("mm/memory_hotplug: embed vmem_altmap details in memory block")
Signed-off-by: Georgi Djakov <georgi.djakov@oss.qualcomm.com>
Acked-by: Oscar Salvador (SUSE) <osalvador@kernel.org>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Richard Cheng <icheng@nvidia.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Georgi Djakov <djakov@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index d31a421f74832c05c480ddbaf03425ffd0332cca..b318344426fabc09eb1574bd52b969be85b0fce1 100644 (file)
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -797,7 +797,6 @@ static int add_memory_block(unsigned long block_id, int nid, unsigned long state
        mem->start_section_nr = block_id * sections_per_block;
        mem->state = state;
        mem->nid = nid;
-       mem->altmap = altmap;
        INIT_LIST_HEAD(&mem->group_next);
 
 #ifndef CONFIG_NUMA
@@ -815,6 +814,8 @@ static int add_memory_block(unsigned long block_id, int nid, unsigned long state
        if (ret)
                return ret;
 
+       mem->altmap = altmap;
+
        if (group) {
                mem->group = group;
                list_add(&mem->group_next, &group->memory_blocks);