[PATCH v3 00/10] mm/vmalloc: fix up vmap error handling

[Hao Ge]

__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.

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. Patches 3 to 7
clean up the range checks and error reporting: unaligned ranges are
clamped or rejected, the callers get the real error code instead of
a flat -ENOMEM, and the cache is only flushed once the mapping
succeeded. Patch 8 adds the rollback
to __vmap_pages_range_noflush() and vmap_page_range(). Patches 9 and
10 drop the powerpc and percpu cleanups that are not needed anymore.

Changes since v2:
- new patches 3 to 7 fix the range checks and the error reporting;
  the empty range check of v2's patch 3 moved into patch 6
- patch 8 (was patch 3) skips cond_resched() in the rollback when
  the caller's gfp mask cannot block
- commit messages reworded

[1] https://lore.kernel.org/all/20260915070001.113559-3-hao.ge@xxxxxxxxx/

v2 link: https://lore.kernel.org/all/20261019054531.87652-1-hao.ge@xxxxxxxxx/
v1 link: https://lore.kernel.org/all/20261009063619.112313-1-hao.ge@xxxxxxxxx/

Hao Ge (10):
  mm/kmsan: undo the shadow mapping when the origin mapping fails
  mm/kmsan: skip vunmap_range_noflush when KMSAN is disabled
  mm/vmalloc: clamp an unaligned range in vunmap_pte_range()
  mm/vmalloc: propagate errors in vmap_pages_p*d_range()
  mm/vmalloc: reject an unaligned range in vmap_pages_pte_range()
  mm/vmalloc: reject empty and unaligned ranges in
    __vmap_pages_range_noflush()
  mm/vmalloc: only flush the cache after the vmap succeeded
  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 +-
 include/linux/kmsan.h            |   8 +-
 mm/kmsan/hooks.c                 |  21 ++++--
 mm/kmsan/shadow.c                |   9 ++-
 mm/percpu-vm.c                   |   5 +-
 mm/vmalloc.c                     | 125 ++++++++++++++++++++++---------
 mm/vmalloc.h                     |   6 +-
 8 files changed, 127 insertions(+), 56 deletions(-)

-- 
2.25.1