ARM: 9524/1: mm: align hugetlb mappings to the huge page size

mmap(MAP_HUGETLB) on 32-bit Arm can return an address which is not
aligned to the huge page size. In a QEMU virt guest, unmapping the VMA
then hits the alignment check in __unmap_hugepage_range():

  kernel BUG at mm/hugetlb.c:5213!
  Internal error: Oops - BUG: 0 [#1] SMP ARM
  PC is at __unmap_hugepage_range+0x540/0x584
  LR is at __zap_vma_range+0x13a0/0x1410

Commit 7bd3f1e1a9ae ("mm: make hugetlb mappings go through
mm_get_unmapped_area_vmflags") made hugetlb mappings use the
architecture's arch_get_unmapped_area(). The generic implementations
handle hugetlb alignment, but the Arm implementations only account for
the optional SHMLBA cache-colouring constraint. A 4 KiB-page kernel can
therefore align the mapping to 4 KiB or 16 KiB instead of the required
2 MiB.

Set the alignment mask from the file's hstate for hugetlb mappings in
both Arm implementations. Huge-page alignment also satisfies the
SHMLBA constraint.

Assisted-by: LLM

Fixes: 7bd3f1e1a9ae ("mm: make hugetlb mappings go through mm_get_unmapped_area_vmflags")
Cc: stable@vger.kernel.org
Acked-by: Muchun Song <muchun.song@linux.dev>
Link: https://lore.kernel.org/r/20260901085740.66283-1-kmehltretter@gmail.com/
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

0 files changed, 0 insertions, 0 deletions