Re: [PATCH v9 3/7] KVM: arm64: Support FFA_NOTIFICATION_UNBIND in host handler

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] do_ffa_notif_unbind improperly restricts the host to only unbind notifications where it is the receiver, preventing it from unbinding notifications it sent.
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commit c6b253b0c883368d7d43d8e94ff20acf54cb8109
Author: Sebastian Ene <sebastianene@google.com>

KVM: arm64: Support FFA_NOTIFICATION_UNBIND in host handler

This commit adds support for the FFA_NOTIFICATION_UNBIND hypercall in the
host handler, verifying arguments and forwarding the message to Trustzone.

> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index 89872e12f9d45..a1ba4463d1ef7 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
[ ... ]
> @@ -913,6 +912,27 @@ static void do_ffa_notif_bind(struct arm_smccc_1_2_regs *res,
>  	hyp_smccc_1_2_smc(args, res);
>  }
>  
> +static void do_ffa_notif_unbind(struct arm_smccc_1_2_regs *res,
> +				struct kvm_cpu_context *ctxt)
> +{
> +	DECLARE_REG(u32, endp_id, ctxt, 1);
> +	DECLARE_REG(u32, reserved, ctxt, 2);
> +	struct arm_smccc_1_2_regs *args;
> +
> +	if (reserved) {
> +		ffa_to_smccc_res(res, FFA_RET_INVALID_PARAMETERS);
> +		return;
> +	}
> +
> +	if (FIELD_GET(FFA_NOTIF_RECEIVER_ENDP_MASK, endp_id) != HOST_FFA_ID) {
> +		ffa_to_smccc_res(res, FFA_RET_INVALID_PARAMETERS);
> +		return;
> +	}

[Severity: Medium]
Does this check improperly restrict the host to only unbind notifications
where it is the receiver?

The FF-A 1.1 specification explicitly permits either the sender or receiver
to unbind a notification. By unconditionally rejecting the hypercall when
the receiver ID does not match HOST_FFA_ID, this prevents the host (acting
as a sender) from unbinding a notification it bound to an SP.

> +
> +	args = (void *)&ctxt->regs.regs[0];
> +	hyp_smccc_1_2_smc(args, res);
> +}
> +

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Sashiko AI review · https://sashiko.dev/#/patchset/20260907171930.4037166-1-sebastianene@google.com?part=3