Re: [PATCH v3 1/1] mm/memory: constrain generic_access_phys() to page boundary

["David Hildenbrand (Arm)" <david@kernel.org>]

On 9/10/26 05:42, Ren Wei wrote:
> From: Luxiao Xu <rakukuip@gmail.com>
> 
> generic_access_phys() improperly validates the memory access range: it
> only validates the start address using follow_pfnmap_start() and passes
> PAGE_ALIGN(len + offset) to ioremap_prot().
> 
> This poses two problems:
> 1. In PFNMAP VMAs, consecutive virtual pages are not guaranteed to be
>    physically contiguous, and individual PTEs may have different access
>    permissions or writability.
> 2. The mapping may cross VMA boundaries if len extends beyond vma->vm_end.
> 
> Constrain the access in generic_access_phys() to at most the current page
> boundary (PAGE_SIZE - offset) and map only a single PAGE_SIZE via
> ioremap_prot(). Since the caller __access_remote_vm() already loops over
> the requested length and handles partial transfers, it will naturally
> iterate over the remaining pages.
> 
> Also add a missing (resource_size_t) cast during PFN re-validation to avoid
> truncation on 32-bit PAE systems.
> 
> Fixes: 9cb12d7b4cca ("mm/memory.c: actually remap enough memory")
> Cc: stable@vger.kernel.org
> Reported-by: Vega <vega@nebusec.ai>
> Assisted-by: LLM
> Suggested-by: David Hildenbrand <david@kernel.org>
> Signed-off-by: Luxiao Xu <rakukuip@gmail.com>
> Signed-off-by: Ren Wei <weir@nebusec.ai>
> ---

Yes, LGTM!

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

-- 
Cheers,

David