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[146.148.11.143]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-46666c579dfsm25252029f8f.31.2026.06.22.04.22.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Jun 2026 04:22:34 -0700 (PDT) Date: Mon, 22 Jun 2026 11:22:31 +0000 From: Sebastian Ene To: Vincent Donnefort Cc: catalin.marinas@arm.com, oupton@kernel.org, sudeep.holla@kernel.org, will@kernel.org, jens.wiklander@linaro.org, joey.gouly@arm.com, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, android-kvm@google.com, maz@kernel.org, mrigendra.chaubey@gmail.com, op-tee@lists.trustedfirmware.org, perlarsen@google.com, seiden@linux.ibm.com, smostafa@google.com, sumit.garg@kernel.org, suzuki.poulose@arm.com, yuzenghui@huawei.com Subject: Re: [PATCH v7 5/7] KVM: arm64: Validate the offset to the mem access descriptor Message-ID: References: <20260617145130.3729015-1-sebastianene@google.com> <20260617145130.3729015-6-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 Mon, Jun 22, 2026 at 09:23:26AM +0000, Sebastian Ene wrote: > On Thu, Jun 18, 2026 at 05:56:24PM +0100, Vincent Donnefort wrote: > > On Wed, Jun 17, 2026 at 02:51:28PM +0000, Sebastian Ene wrote: > > > Prevent the pKVM hypervisor from making assumptions that the > > > endpoint memory access descriptor (EMAD) comes right after the > > > FF-A memory region header. > > > 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 from 1.1 onward: > > > Type | Field name | Offset > > > [ Header | ffa_mem_region | 0 > > > EMAD 1 | ffa_mem_region_attributes) | ffa_mem_region.ep_mem_offset > > > ] > > > Verify that the offset to the first endpoint memory access descriptor > > > is within the mailbox buffer bounds. > > > > > > Also, fix one hardcoded sizeof(struct ffa_mem_region_attributes) that > > > should be replaced ffa_emad_size_get() for compatibility with FFA v1.0. > > > > > > Fixes: 42fb33dde42b ("KVM: arm64: Use FF-A 1.1 with pKVM") > > > Signed-off-by: Sebastian Ene > > > Signed-off-by: Mostafa Saleh > > > --- > > > arch/arm64/kvm/hyp/nvhe/ffa.c | 29 +++++++++++++++++++++-------- > > > 1 file changed, 21 insertions(+), 8 deletions(-) > > > > > > diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c > > > index 2d211661952e..1a2abd0154c6 100644 > > > --- a/arch/arm64/kvm/hyp/nvhe/ffa.c > > > +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c > > > @@ -476,11 +476,14 @@ static void __do_ffa_mem_xfer(const u64 func_id, > > > DECLARE_REG(u32, fraglen, ctxt, 2); > > > DECLARE_REG(u64, addr_mbz, ctxt, 3); > > > DECLARE_REG(u32, npages_mbz, ctxt, 4); > > > + u32 offset, nr_ranges, checked_offset, em_mem_access_off; > > > struct ffa_mem_region_attributes *ep_mem_access; > > > struct ffa_composite_mem_region *reg; > > > struct ffa_mem_region *buf; > > > - u32 offset, nr_ranges, checked_offset; > > > int ret = 0; > > > + size_t mem_region_len = !FFA_MEM_REGION_HAS_EP_MEM_OFFSET(hyp_ffa_version) ? > > > + offsetof(struct ffa_mem_region, ep_mem_offset) : > > > + sizeof(struct ffa_mem_region); While talking with Vincent about this change, we agreed that it would be easier to introduce a helper that will get the size of the struct ffa_mem_region which is different based on the ff-a version. This would hopefully increase the readability of this. The description of the struct ffa_mem_region can be found in (Table 5.19: Lend, donate or share memory transaction descriptor) from DEN0077A. I will spin a new version to address this and collect the review tags. > > > > > > if (addr_mbz || npages_mbz || fraglen > len || > > > fraglen > KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE) { > > > @@ -488,8 +491,7 @@ static void __do_ffa_mem_xfer(const u64 func_id, > > > goto out; > > > } > > > > > > - if (fraglen < sizeof(struct ffa_mem_region) + > > > - sizeof(struct ffa_mem_region_attributes)) { > > > + if (fraglen < mem_region_len + ffa_emad_size_get(hyp_ffa_version)) { > > > > Can't we replace mem_region_len with ffa_mem_desc_offset()? that pretty much > > looks like the same thing. > > > > We can't because `ffa_mem_desc_offset` dereferences struct > ffa_mem_region to extract ep_mem_offset as per the latest updates. > > > > > > ret = FFA_RET_INVALID_PARAMETERS; > > > goto out; > > > } > > > @@ -508,8 +510,13 @@ static void __do_ffa_mem_xfer(const u64 func_id, > > > buf = hyp_buffers.tx; > > > memcpy(buf, host_buffers.tx, fraglen); > > > > > > - ep_mem_access = (void *)buf + > > > - ffa_mem_desc_offset(buf, 0, hyp_ffa_version); > > > + em_mem_access_off = ffa_mem_desc_offset(buf, 0, hyp_ffa_version); > > > + if ((u64)em_mem_access_off + ffa_emad_size_get(hyp_ffa_version) > fraglen) { > > > > This check looks like ffa_mem_desc_offset() with count to 1. > > > > > > > + ret = FFA_RET_INVALID_PARAMETERS; > > > + goto out_unlock; > > > + } > > > + > > > + ep_mem_access = (void *)buf + em_mem_access_off; > > > offset = ep_mem_access->composite_off; > > > if (!offset || buf->ep_count != 1 || buf->sender_id != HOST_FFA_ID) { > > > ret = FFA_RET_INVALID_PARAMETERS; > > > @@ -574,9 +581,9 @@ static void do_ffa_mem_reclaim(struct arm_smccc_1_2_regs *res, > > > DECLARE_REG(u32, handle_lo, ctxt, 1); > > > DECLARE_REG(u32, handle_hi, ctxt, 2); > > > DECLARE_REG(u32, flags, ctxt, 3); > > > + u32 offset, len, fraglen, fragoff, em_mem_access_off; > > > struct ffa_mem_region_attributes *ep_mem_access; > > > struct ffa_composite_mem_region *reg; > > > - u32 offset, len, fraglen, fragoff; > > > struct ffa_mem_region *buf; > > > int ret = 0; > > > u64 handle; > > > @@ -599,8 +606,14 @@ static void do_ffa_mem_reclaim(struct arm_smccc_1_2_regs *res, > > > len = res->a1; > > > fraglen = res->a2; > > > > > > - ep_mem_access = (void *)buf + > > > - ffa_mem_desc_offset(buf, 0, hyp_ffa_version); > > > + em_mem_access_off = ffa_mem_desc_offset(buf, 0, hyp_ffa_version); > > > + if ((u64)em_mem_access_off + ffa_emad_size_get(hyp_ffa_version) > fraglen) { > > > > ditto. ffa_mem_desc_offset() > > > > > + ret = FFA_RET_INVALID_PARAMETERS; > > > + ffa_rx_release(res); > > > + goto out_unlock; > > > + } > > > + > > > + ep_mem_access = (void *)buf + em_mem_access_off; > > > offset = ep_mem_access->composite_off; > > > /* > > > * We can trust the SPMD to get this right, but let's at least > > > -- > > > 2.54.0.1136.gdb2ca164c4-goog > > > > > Thanks, > Sebastian