riscv: handle VM_FAULT_[HWPOISON|HWPOISON_LARGE] faults instead of panicking

Patch series "Fix set_huge_pte_at()".

A recent report [1] from Ryan for arm64 revealed that we do not handle
swap entries when setting a hugepage backed by a NAPOT region (the contpte
riscv equivalent).

As explained in [1], the issue was discovered by a new test in kselftest
which uses poison entries, but the symptoms are different from arm64 though:

- the riscv kernel bugs because we do not handle VM_FAULT_HWPOISON*,
  this is fixed by patch 1,
- after that, the test passes because the first pte_napot() fails (the
  poison entry does not have the N bit set), and then we only set the
  first page table entry covering the NAPOT hugepage, which is enough
  for hugetlb_fault() to correctly raise a VM_FAULT_HWPOISON wherever we
  write in this mapping since only this first page table entry is
  checked
  (see https://elixir.bootlin.com/linux/v6.6-rc3/source/mm/hugetlb.c#L6071).
  But this seems fragile so patch 2 sets all page table entries of a
  NAPOT mapping.

[1]: https://lore.kernel.org/linux-arm-kernel/[email protected]/


This patch (of 2):

We used to panic when such faults were encountered but we should handle
those faults gracefully for userspace by sending a SIGBUS to the process,
like most architectures do.

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Alexandre Ghiti <[email protected]>
Acked-by: Palmer Dabbelt <[email protected]>
Cc: Albert Ou <[email protected]>
Cc: Andrew Jones <[email protected]>
Cc: Conor Dooley <[email protected]>
Cc: Paul Walmsley <[email protected]>
Cc: Qinglin Pan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions