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

[Catalin Marinas <catalin.marinas@arm.com>]

On Fri, Feb 21, 2025 at 04:17:09PM +0100, Greg Kroah-Hartman wrote:
> 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.
> 
> Now queued up, thanks.

Thanks Greg.

-- 
Catalin