Re: [PATCH] arm64: kvm: Fix potential overflow in len

[Oliver Upton]

On Sat, Dec 28, 2024 at 02:01:27AM +0000, Steven Davis wrote:
> The MMIO sign-extension logic in kvm_handle_mmio_return can
> trigger an integer overflow or undefined behavior when len
> is invalid (e.g., len == 0 or len exceeds the size of unsigned
> long). Specifically, the expression (len * 8) - 1 may result
> in an out-of-bounds shift in the computation of the mask.

I don't believe we need this. len is known to be nonzero and at most 8,
which is already being tested for in the existing condition. See the
definition of kvm_vcpu_dabt_get_as() if you're curious why that is.

-- 
Thanks,
Oliver