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[47.55.120.4]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8846e447272sm148376376d6.5.2025.11.26.10.01.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Nov 2025 10:01:08 -0800 (PST) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1vOJpD-000000033ob-2pNk; Wed, 26 Nov 2025 14:01:07 -0400 Date: Wed, 26 Nov 2025 14:01:07 -0400 From: Jason Gunthorpe To: Alex Mastro , Alex Williamson Cc: Sumit Semwal , Christian =?utf-8?B?S8O2bmln?= , Leon Romanovsky , Kevin Tian , Nicolin Chen , linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Ankit Agrawal Subject: Re: [PATCH] dma-buf: fix integer overflow in fill_sg_entry() for buffers >= 8GiB Message-ID: <20251126180107.GA542915@ziepe.ca> References: <20251125-dma-buf-overflow-v1-1-b70ea1e6c4ba@fb.com> Precedence: bulk X-Mailing-List: kvm@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: <20251125-dma-buf-overflow-v1-1-b70ea1e6c4ba@fb.com> On Tue, Nov 25, 2025 at 05:11:18PM -0800, Alex Mastro wrote: > fill_sg_entry() splits large DMA buffers into multiple scatter-gather > entries, each holding up to UINT_MAX bytes. When calculating the DMA > address for entries beyond the second one, the expression (i * UINT_MAX) > causes integer overflow due to 32-bit arithmetic. > > This manifests when the input arg length >= 8 GiB results in looping for > i >= 2. > > Fix by casting i to dma_addr_t before multiplication. > > Fixes: 3aa31a8bb11e ("dma-buf: provide phys_vec to scatter-gather mapping routine") > Signed-off-by: Alex Mastro > --- > More color about how I discovered this in [1] for the commit at [2]: > > [1] https://lore.kernel.org/all/aSZHO6otK0Heh+Qj@devgpu015.cco6.facebook.com > [2] https://lore.kernel.org/all/20251120-dmabuf-vfio-v9-6-d7f71607f371@nvidia.com > --- > drivers/dma-buf/dma-buf-mapping.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Reviewed-by: Jason Gunthorpe AlexW, can you pick this up? Thanks, Jason