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[146.148.11.143]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-46c221d9371sm24794653f8f.21.2026.06.26.02.24.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Jun 2026 02:24:56 -0700 (PDT) Date: Fri, 26 Jun 2026 09:24:52 +0000 From: Sebastian Ene To: Will Deacon Cc: catalin.marinas@arm.com, maz@kernel.org, oupton@kernel.org, joey.gouly@arm.com, korneld@google.com, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, android-kvm@google.com, mrigendra.chaubey@gmail.com, perlarsen@google.com, suzuki.poulose@arm.com, vdonnefort@google.com, yuzenghui@huawei.com Subject: Re: [PATCH v6 7/7] KVM: arm64: Enforce strict SBZ checks in the FF-A proxy Message-ID: References: <20260626074545.433234-1-sebastianene@google.com> <20260626074545.433234-8-sebastianene@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Jun 26, 2026 at 10:11:14AM +0100, Will Deacon wrote: > On Fri, Jun 26, 2026 at 07:45:45AM +0000, Sebastian Ene wrote: > > Introduce a helper method ffa_check_unused_args_sbz to enforce strict > > arguments checking when the hypervisor acts as a relayer between the > > host and Trustzone. > > > > Signed-off-by: Sebastian Ene > > Reviewed-by: Vincent Donnefort > > --- > > arch/arm64/kvm/hyp/nvhe/ffa.c | 96 ++++++++++++++++++++++++++++++++++- > > 1 file changed, 95 insertions(+), 1 deletion(-) > > > > diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c > > index 712811e89435..bd50ddc5b61c 100644 > > --- a/arch/arm64/kvm/hyp/nvhe/ffa.c > > +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c > > @@ -74,6 +74,21 @@ static u32 hyp_ffa_version; > > static bool has_version_negotiated; > > static hyp_spinlock_t version_lock; > > > > +static bool ffa_check_unused_args_sbz(struct kvm_cpu_context *ctxt, int first_reg) > > +{ > > + DECLARE_REG(u32, func_id, ctxt, 0); > > + int reg, end_reg = 7; > > + > > + if (FFA_MINOR_VERSION(hyp_ffa_version) >= 2) > > + end_reg = ARM_SMCCC_IS_64(func_id) ? 17 : 7; > > This looks like an accident waiting to happen if we don't check the major > number as well. > > I think you should just check: > > if (hyp_ffa_version >= FFA_VERSION_1_2) > > instead. > > You should also add a comment. We restrict hyp_ffa_version major to 1.0 here https://elixir.bootlin.com/linux/v7.1.1/source/arch/arm64/kvm/hyp/nvhe/ffa.c#L962 but since this is an easy fix I will include it. > > Will Sebastian