Re: [PATCH] iommu/intel: Fix __domain_mapping()'s usage of switch_to_super_page()

[Baolu Lu]

On 8/26/25 22:38, Eugene Koira wrote:
> switch_to_super_page() assumes the memory range it's working on is aligned
> to the target large page level. Unfortunately, __domain_mapping() doesn't
> take this into account when using it, and will pass unaligned ranges
> ultimately freeing a PTE range larger than expected.
>
> Take for example a mapping with the following iov_pfn range [0x3fe400,
> 0x4c0600], which should be backed by the following mappings:
>
>     iov_pfn [0x3fe400, 0x3fffff] covered by 2MiB pages
>     iov_pfn [0x400000, 0x4bffff] covered by 1GiB pages
>     iov_pfn [0x4c0000, 0x4c05ff] covered by 2MiB pages
>
> Under this circumstance, __domain_mapping() will pass [0x400000, 0x4c05ff]
> to switch_to_super_page() at a 1 GiB granularity, which will in turn
> free PTEs all the way to iov_pfn 0x4fffff.
>
> Mitigate this by rounding down the iov_pfn range passed to
> switch_to_super_page() in __domain_mapping()
> to the target large page level.
>
> Additionally add range alignment checks to switch_to_super_page.
>
> Fixes: 9906b9352a35 ("iommu/vt-d: Avoid duplicate removing in __domain_mapping()")
> Signed-off-by: Eugene Koira<eugkoira@xxxxxxxxxx>
> Cc:stable@xxxxxxxxxxxxxxx
> ---
>   drivers/iommu/intel/iommu.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)

Queued for v6.17-rc. Thank you!

Thanks,
baolu