[PATCH v4 0/9] mm/vmalloc: fix up vmap error handling

[Hao Ge <hao.ge@linux.dev>]

__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 warning in vmap_pages_pte_range(). A leftover huge pmd is worse.
During the retry, vmap_try_huge_pmd() calls pmd_free_pte_page() on
it, and the x86 implementation cannot tell a leaf entry from a page
table and frees the mapped page.

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 5 bug
out on an unaligned range at the entry of the three range walkers.
Patch 6 only flushes the cache once the mapping succeeded. Patch 7
adds the rollback to __vmap_pages_range_noflush() and
vmap_page_range(). Patches 8 and 9 drop the powerpc and percpu
cleanups that are not needed anymore.

Changes since v3:
- drop v3 patch 3. The clamp papered over the caller bug, a bad
  range now BUG_ONs at the unmap entry
- drop v3 patch 4. The reworked walk (24bbe1c56f63a) propagates
  the errors already
- drop v3 patch 6. The walk below checks the range already
- the map side checks moved from the pte level to the entries of
  vmap_range_noflush() and the walk, and became BUG_ON, in line
  with the unmap side
- rebase onto the walk rework, commit messages updated accordingly

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

v3 link: https://lore.kernel.org/all/20261026080329.140244-1-hao.ge@linux.dev/
v2 link: https://lore.kernel.org/all/20261019054531.87652-1-hao.ge@linux.dev/
v1 link: https://lore.kernel.org/all/20261009063619.112313-1-hao.ge@linux.dev/

Hao Ge (9):
  mm/kmsan: undo the shadow mapping when the origin mapping fails
  mm/kmsan: skip vunmap_range_noflush when KMSAN is disabled
  mm/vmalloc: BUG_ON() on an unaligned range in vmap_range_noflush()
  mm/vmalloc: BUG_ON() on an unaligned range in
    vmap_pages_range_noflush_walk()
  mm/vmalloc: BUG_ON() on an unaligned range in __vunmap_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                     | 75 ++++++++++++++++++++++++--------
 mm/vmalloc.h                     |  6 ++-
 8 files changed, 94 insertions(+), 39 deletions(-)

-- 
2.25.1