Re: [PATCH v2] mm/madvise: reject invalid process_madvise() advice for zero-length vectors

David Hildenbrand (Arm)
2026-04-27T11:49:53Z

On 4/27/26 11:43, fujunjie wrote:
> process_madvise() used to validate the advice while walking each
> imported iovec. If the vector has zero total length, vector_madvise()
> does not enter the loop and can return success without checking whether
> the advice value is valid.
>
> For a local mm, such as process_madvise(PIDFD_SELF, ...), the remote-only
> process_madvise_remote_valid() check is skipped. As a result, an invalid
> advice can be reported as success when the vector has zero total length.
> This differs from madvise(), which rejects an invalid advice before
> returning success for a zero-length range.
>
> Validate the generic madvise behavior at the syscall-facing entry points
> before any vector walk. In process_madvise(), do this before the
> remote-only advice restriction so unsupported advice is rejected with the
> same priority for local and remote mm. Then keep the per-range helper
> focused on address/length validation, avoiding repeated behavior checks
> for every iovec.
>
> Valid zero-length requests remain no-ops and continue to return 0. Add a
> selftest that covers invalid advice with a zero-length iovec and an empty
> vector, while also checking that a valid zero-length request still
> succeeds.
>
> Fixes: 021781b01275 ("mm/madvise: unrestrict process_madvise() for current process")
> Signed-off-by: fujunjie <fujunjie1@qq.com>
> ---

Next time, please don't send new revisions as reply to previous submissions.

Thanks!

Acked-by: David Hildenbrand (Arm) <david@kernel.org>

--
Cheers,

David