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Alistair Popple
bf477abd44
[ Upstream commit744dd97752] Patch series "Minor hmm_test fixes and cleanups". Two bugfixes a cleanup for the HMM kernel selftests. These were mostly reported by Zenghui Yu with special thanks to Lorenzo for analysing and pointing out the problems. This patch (of 3): When dmirror_fops_release() is called it frees the dmirror struct but doesn't migrate device private pages back to system memory first. This leaves those pages with a dangling zone_device_data pointer to the freed dmirror. If a subsequent fault occurs on those pages (eg. during coredump) the dmirror_devmem_fault() callback dereferences the stale pointer causing a kernel panic. This was reported [1] when running mm/ksft_hmm.sh on arm64, where a test failure triggered SIGABRT and the resulting coredump walked the VMAs faulting in the stale device private pages. Fix this by calling dmirror_device_evict_chunk() for each devmem chunk in dmirror_fops_release() to migrate all device private pages back to system memory before freeing the dmirror struct. The function is moved earlier in the file to avoid a forward declaration. Link: https://lore.kernel.org/20260331063445.3551404-1-apopple@nvidia.com Link: https://lore.kernel.org/20260331063445.3551404-2-apopple@nvidia.com Fixes:b2ef9f5a5c("mm/hmm/test: add selftest driver for HMM") Signed-off-by: Alistair Popple <apopple@nvidia.com> Reported-by: Zenghui Yu <zenghui.yu@linux.dev> Closes: https://lore.kernel.org/linux-mm/8bd0396a-8997-4d2e-a13f-5aac033083d7@linux.dev/ Reviewed-by: Balbir Singh <balbirs@nvidia.com> Tested-by: Zenghui Yu <zenghui.yu@linux.dev> Cc: David Hildenbrand <david@kernel.org> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Leon Romanovsky <leon@kernel.org> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Zenghui Yu <zenghui.yu@linux.dev> Cc: Matthew Brost <matthew.brost@intel.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> [ kept the existing simpler `dmirror_device_evict_chunk()` body instead of the upstream compound-folio version ] Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>