Re: [PATCH] KVM: arm64: Validate the FF-A memory access descriptor placement

M.samet Duman
2026-04-27T12:48:50Z

I haven't tested this, but the change looks reasonable to me.

Samet

> 2026. 4. 22. 오후 1:27, Sebastian Ene <sebastianene@google.com> 작성:
>
> ﻿Prevent the pKVM hypervisor from making assumptions that the
> endpoint memory access descriptor (EMAD) comes right after the
> FF-A memory region header and enforce a strict placement for it
> when validating an FF-A memory lend/share transaction.
>
> Prior to FF-A version 1.1 the header of the memory region
> didn't contain an offset to the endpoint memory access descriptor.
> The layout of a memory transaction looks like this:
>
> Field name | Offset
> -- 0
> [ Header (ffa_mem_region) |__ ep_mem_offset
> EMAD 1 (ffa_mem_region_attributes) |
> ]
>
> Reject the host from specifying a memory access descriptor offset
> that is different than the size of the memory region header.
>
> Cc: stable@vger.kernel.org
> Fixes: 42fb33dde42b ("KVM: arm64: Use FF-A 1.1 with pKVM")
> Signed-off-by: Sebastian Ene <sebastianene@google.com>
> ---
> arch/arm64/kvm/hyp/nvhe/ffa.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index 94161ea1cd60..0703c0ad8dff 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -508,6 +508,12 @@ static void __do_ffa_mem_xfer(const u64 func_id,
> buf = hyp_buffers.tx;
> memcpy(buf, host_buffers.tx, fraglen);
>
> + if (FFA_MEM_REGION_HAS_EP_MEM_OFFSET(hyp_ffa_version) &&
> + buf->ep_mem_offset != sizeof(struct ffa_mem_region)) {
> + ret = FFA_RET_INVALID_PARAMETERS;
> + goto out_unlock;
> + }
> +
> ep_mem_access = (void *)buf +
> ffa_mem_desc_offset(buf, 0, hyp_ffa_version);
> offset = ep_mem_access->composite_off;
> --
> 2.54.0.rc1.555.g9c883467ad-goog
>
>