linux-kernel - Re: [PATCH v1 1/1] dmaengine: stm32-dmamux: fix a potential buffer overflow

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Message-ID: <20180322052150.GB15443@localhost>
Date:   Thu, 22 Mar 2018 10:51:50 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Pierre-Yves MORDRET <pierre-yves.mordret@...com>
Cc:     Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Dan Williams <dan.j.williams@...el.com>,
        M'boumba Cedric Madianga <cedric.madianga@...il.com>,
        dmaengine@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/1] dmaengine: stm32-dmamux: fix a potential buffer
 overflow

On Tue, Mar 13, 2018 at 05:55:35PM +0100, Pierre-Yves MORDRET wrote:
> The bitfield dma_inuse is allocated of size dma_requests bits, thus a
> valid bit address is from 0 to (dma_requests - 1).
> When find_first_zero_bit() fails, it returns dma_requests as invalid
> address.
> Using such address for the following set_bit() is incorrect and, if
> dma_requests is a multiple of BITS_PER_LONG, it will cause a buffer
> overflow.
> Currently this driver is only used in DT stm32h743.dtsi where a safe value
> dma_requests=16 is not triggering the buffer overflow.
> 
> Fixed by checking the return value of find_first_zero_bit() _before_
> using it.

Applied, thanks

-- 
~Vinod