linux-kernel - Re: [PATCH] dma-buf: fix integer overflow in fill_sg

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Message-ID: <20251126071810.GF12483@unreal>
Date: Wed, 26 Nov 2025 09:18:10 +0200
From: Leon Romanovsky <leon@...nel.org>
To: Alex Mastro <amastro@...com>
Cc: Sumit Semwal <sumit.semwal@...aro.org>,
	Christian König <christian.koenig@....com>,
	Alex Williamson <alex@...zbot.org>, Jason Gunthorpe <jgg@...pe.ca>,
	Kevin Tian <kevin.tian@...el.com>,
	Nicolin Chen <nicolinc@...dia.com>, linux-media@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	Ankit Agrawal <ankita@...dia.com>
Subject: Re: [PATCH] dma-buf: fix integer overflow in fill_sg_entry() for
 buffers >= 8GiB

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 <amastro@...com>
> ---
> 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(-)
> 

Thanks,
Reviewed-by: Leon Romanovsky <leon@...nel.org>