Re: [PATCH stable 5.10.y-6.12.y] arm64: mte: Do not allow PROT_MTE on MAP_HUGETLB user mappings

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Feb 20, 2025 at 03:58:01PM +0000, Catalin Marinas wrote:
> PROT_MTE (memory tagging extensions) is not supported on all user mmap()
> types for various reasons (memory attributes, backing storage, CoW
> handling). The arm64 arch_validate_flags() function checks whether the
> VM_MTE_ALLOWED flag has been set for a vma during mmap(), usually by
> arch_calc_vm_flag_bits().
> 
> Linux prior to 6.13 does not support PROT_MTE hugetlb mappings. This was
> added by commit 25c17c4b55de ("hugetlb: arm64: add mte support").
> However, earlier kernels inadvertently set VM_MTE_ALLOWED on
> (MAP_ANONYMOUS | MAP_HUGETLB) mappings by only checking for
> MAP_ANONYMOUS.
> 
> Explicitly check MAP_HUGETLB in arch_calc_vm_flag_bits() and avoid
> setting VM_MTE_ALLOWED for such mappings.
> 
> Fixes: 9f3419315f3c ("arm64: mte: Add PROT_MTE support to mmap() and mprotect()")
> Cc: <stable@vger.kernel.org> # 5.10.x-6.12.x
> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
> ---
> 
> Hi Greg,
> 
> This patch applies cleanly on top of the stable-rc/linux-6.12.y to
> 5.10.y LTS, so I'm only sending it once. It's not for 6.13 onwards since
> those kernels support hugetlbfs with MTE.

Thanks for this, I'll queue it up after the next round of releases.

greg k-h