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Thu, 21 May 2026 08:28:46 +0000 Date: Thu, 21 May 2026 09:28:46 +0100 Message-ID: <86ldddw4ht.wl-maz@kernel.org> From: Marc Zyngier To: Mostafa Saleh Cc: op-tee@lists.trustedfirmware.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, oupton@kernel.org, joey.gouly@arm.com, suzuki.poulose@arm.com, catalin.marinas@arm.com, jens.wiklander@linaro.org, sumit.garg@kernel.org, sebastianene@google.com, vdonnefort@google.com, sudeep.holla@kernel.org Subject: Re: [PATCH v4 4/5] KVM: arm64: Fix bounds checking in do_ffa_mem_reclaim() In-Reply-To: <20260520204948.2440882-5-smostafa@google.com> References: <20260520204948.2440882-1-smostafa@google.com> <20260520204948.2440882-5-smostafa@google.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: smostafa@google.com, op-tee@lists.trustedfirmware.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, oupton@kernel.org, joey.gouly@arm.com, suzuki.poulose@arm.com, catalin.marinas@arm.com, jens.wiklander@linaro.org, sumit.garg@kernel.org, sebastianene@google.com, vdonnefort@google.com, sudeep.holla@kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, 20 May 2026 21:49:47 +0100, Mostafa Saleh wrote: > > Sashiko (locally) reports out of bound write possiblity if SPMD > returns an invalid data. > > While SPMD is considered trusted, pKVM does some basic checks, > for offset to be less than or equal len. > > However, that is incorrect as even if the offset is smaller than > len pKVM can still access out of bound memory in the next > ffa_host_unshare_ranges(). > > Split this check into 2: > 1- Check that the fixed portion of the descriptor fits. > 2- After getting reg, check the variable array size addr_range_cnt > fits. > > Signed-off-by: Mostafa Saleh > --- > arch/arm64/kvm/hyp/nvhe/ffa.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c > index 1af722771178..e6aa2bfa63b1 100644 > --- a/arch/arm64/kvm/hyp/nvhe/ffa.c > +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c > @@ -607,7 +607,7 @@ static void do_ffa_mem_reclaim(struct arm_smccc_1_2_regs *res, > * check that we end up with something that doesn't look _completely_ > * bogus. > */ > - if (WARN_ON(offset > len || > + if (WARN_ON(offset + CONSTITUENTS_OFFSET(0) > len || > fraglen > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE)) { Do you really want to keep this a WARN_ON(), given that this results in a panic in most pKVM configurations? Thanks, M. -- Without deviation from the norm, progress is not possible.