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[34.38.181.8]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48fce065732sm43837465e9.6.2026.05.13.06.34.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 May 2026 06:34:48 -0700 (PDT) Date: Wed, 13 May 2026 13:34:42 +0000 From: Mostafa Saleh To: Sebastian Ene Cc: catalin.marinas@arm.com, maz@kernel.org, oupton@kernel.org, sudeep.holla@kernel.org, will@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 v3 1/2] firmware: arm_ffa: Fix Endpoint Memory Access Descriptor offset calculation Message-ID: References: <20260512124442.1899107-1-sebastianene@google.com> <20260512124442.1899107-2-sebastianene@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260512124442.1899107-2-sebastianene@google.com> On Tue, May 12, 2026 at 12:44:41PM +0000, Sebastian Ene wrote: > Use the descriptor's `ep_mem_offset` to calculate the start of the endpoint > memory access array and to comply with the FF-A spec instead of defaulting > to `sizeof(struct ffa_mem_region)`. > This requires moving `ffa_mem_region_additional_setup()` earlier in the setup > flow. > Also, add sanity checks to ensure the calculated descriptor offsets do not > exceed `max_fragsize`. > > Signed-off-by: Sebastian Ene > --- > drivers/firmware/arm_ffa/driver.c | 14 ++++++++++---- > include/linux/arm_ffa.h | 2 +- > 2 files changed, 11 insertions(+), 5 deletions(-) > > diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c > index eb2782848283..56b166290b24 100644 > --- a/drivers/firmware/arm_ffa/driver.c > +++ b/drivers/firmware/arm_ffa/driver.c > @@ -685,18 +685,25 @@ ffa_setup_and_transmit(u32 func_id, void *buffer, u32 max_fragsize, > struct ffa_composite_mem_region *composite; > struct ffa_mem_region_addr_range *constituents; > struct ffa_mem_region_attributes *ep_mem_access; > - u32 idx, frag_len, length, buf_sz = 0, num_entries = sg_nents(args->sg); > + u32 idx, frag_len, length, buf_sz = 0, num_entries = sg_nents(args->sg), ep_offset; > > mem_region->tag = args->tag; > mem_region->flags = args->flags; > mem_region->sender_id = drv_info->vm_id; > mem_region->attributes = ffa_memory_attributes_get(func_id); > + > + ffa_mem_region_additional_setup(drv_info->version, mem_region); > composite_offset = ffa_mem_desc_offset(buffer, args->nattrs, > drv_info->version); > + if (composite_offset > max_fragsize - sizeof(struct ffa_composite_mem_region)) > + return -ENXIO; nit: This driver seems to use sizeof() with variable name rather than type (except for one place) so it may be good to keep that. > > for (idx = 0; idx < args->nattrs; idx++) { > - ep_mem_access = buffer + > - ffa_mem_desc_offset(buffer, idx, drv_info->version); > + ep_offset = ffa_mem_desc_offset(buffer, idx, drv_info->version); > + if (ep_offset > max_fragsize - sizeof(struct ffa_mem_region_attributes)) > + return -ENXIO; > + > + ep_mem_access = buffer + ep_offset; > ep_mem_access->receiver = args->attrs[idx].receiver; > ep_mem_access->attrs = args->attrs[idx].attrs; > ep_mem_access->composite_off = composite_offset; > @@ -708,7 +715,6 @@ ffa_setup_and_transmit(u32 func_id, void *buffer, u32 max_fragsize, > } > mem_region->handle = 0; > mem_region->ep_count = args->nattrs; > - ffa_mem_region_additional_setup(drv_info->version, mem_region); > > composite = buffer + composite_offset; > composite->total_pg_cnt = ffa_get_num_pages_sg(args->sg); > diff --git a/include/linux/arm_ffa.h b/include/linux/arm_ffa.h > index 81e603839c4a..62d67dae8b70 100644 > --- a/include/linux/arm_ffa.h > +++ b/include/linux/arm_ffa.h > @@ -445,7 +445,7 @@ ffa_mem_desc_offset(struct ffa_mem_region *buf, int count, u32 ffa_version) > if (!FFA_MEM_REGION_HAS_EP_MEM_OFFSET(ffa_version)) > offset += offsetof(struct ffa_mem_region, ep_mem_offset); > else > - offset += sizeof(struct ffa_mem_region); > + offset += buf->ep_mem_offset; Does it make sense to also set buf->ep_mem_offset for the other case in ffa_mem_region_additional_setup() and then add this unconditionally here? Thanks, Mostafa > > return offset; > } > -- > 2.54.0.563.g4f69b47b94-goog >