__vmap_pages_range_noflush() and friends can install some PTEs before failing and leave them mapped, and the kernel callers do not agree on who cleans them up. pcpu_map_pages() and kmsan_ioremap_page_range() roll back what they mapped before the failure, while vm_module_tags_populate() and the __GFP_NOFAIL retry loop in __vmalloc_area_node() rely on the mapping functions cleaning up and do not call anything like vunmap_range() themselves. When the same range is mapped again, the attempt hits the leftovers and fails, with a BUG() in vmap_pte_range() for huge mappings and a warning on the small-page path.
After discussing with Suren and Ulad [1], we move the rollback into the mapping functions. A failed vmap leaves nothing mapped, and the callers no longer clean up after it. [1] https://lore.kernel.org/all/[email protected]/ Patch 1 is the KMSAN part. The shadow and the origin of a range are mapped by two separate calls, so the rollback there has to cover both. Patch 2 is its disabled-KMSAN counterpart. Patch 3 adds the rollback to __vmap_pages_range_noflush() and vmap_page_range(). Patches 4 and 5 drop the powerpc and percpu cleanups that are not needed anymore. Changes since v1: - Add patch 2. Sashiko reported that an empty range that hits patch 3's WARN_ON_ONCE() trips __vunmap_range_noflush()'s BUG_ON() through kmsan_vunmap_range_noflush() when kmsan=0. Patch 2 adds the kmsan_enabled check the unmap side was missing. - Pick up Reviewed-by tags from Suren and Ulad on patches 1, 4 and 5. - Add Cc: stable to patch 3. v1 link: https://lore.kernel.org/all/[email protected]/ Hao Ge (5): mm/kmsan: undo the shadow mapping when the origin mapping fails mm/kmsan: skip vunmap_range_noflush when KMSAN is disabled mm/vmalloc: undo partial mappings inside the mapping functions powerpc: drop redundant unmaps of failed vmap mappings mm/percpu: stop unmapping the CPU that failed to map arch/powerpc/kernel/isa-bridge.c | 5 ++-- arch/powerpc/kernel/pci_64.c | 4 +-- mm/kmsan/hooks.c | 3 +++ mm/kmsan/shadow.c | 4 +++ mm/percpu-vm.c | 5 ++-- mm/vmalloc.c | 44 +++++++++++++++++++++++--------- 6 files changed, 45 insertions(+), 20 deletions(-) -- 2.25.1
