In mremap_dontunmap_partial_mapping_overwrite(), mremap() stores its returned remapped address into remapped_mapping, while the BUG_ON incorrectly checks dest_mapping instead. If mremap() fails, dest_mapping still holds a valid pointer obtained from the prior mmap() call, making this BUG_ON never trigger at all. Correct the check to validate the actual mremap() return value stored in remapped_mapping. Link: https://lore.kernel.org/20260717070251.73212-1-hongfu.li@linux.dev Signed-off-by: Hongfu Li <lihongfu@kylinos.cn> Reviewed-by: SJ Park <sj@kernel.org> Cc: David Hildenbrand <david@kernel.org> Cc: Liam R. Howlett <liam@infradead.org> Cc: Lorenzo Stoakes <ljs@kernel.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Shuah Khan <shuah@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vlastimil Babka <vbabka@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>