linux-kernel - Re: [PATCH net v3] net: ipa: compute DMA pool size properly

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Message-ID: <20230329113620.GO831478@unreal>
Date:   Wed, 29 Mar 2023 14:36:20 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Alex Elder <elder@...aro.org>
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, quic_bjorande@...cinc.com, mbloch@...dia.com,
        caleb.connolly@...aro.org, mka@...omium.org, evgreen@...omium.org,
        andersson@...nel.org, quic_cpratapa@...cinc.com,
        quic_avuyyuru@...cinc.com, quic_jponduru@...cinc.com,
        quic_subashab@...cinc.com, elder@...nel.org,
        netdev@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v3] net: ipa: compute DMA pool size properly

On Tue, Mar 28, 2023 at 11:27:51AM -0500, Alex Elder wrote:
> In gsi_trans_pool_init_dma(), the total size of a pool of memory
> used for DMA transactions is calculated.  However the calculation is
> done incorrectly.
> 
> For 4KB pages, this total size is currently always more than one
> page, and as a result, the calculation produces a positive (though
> incorrect) total size.  The code still works in this case; we just
> end up with fewer DMA pool entries than we intended.
> 
> Bjorn Andersson tested booting a kernel with 16KB pages, and hit a
> null pointer derereference in sg_alloc_append_table_from_pages(),
> descending from gsi_trans_pool_init_dma().  The cause of this was
> that a 16KB total size was going to be allocated, and with 16KB
> pages the order of that allocation is 0.  The total_size calculation
> yielded 0, which eventually led to the crash.
> 
> Correcting the total_size calculation fixes the problem.
> 
> Reported-by: Bjorn Andersson <quic_bjorande@...cinc.com>
> Tested-by: Bjorn Andersson <quic_bjorande@...cinc.com>
> Fixes: 9dd441e4ed57 ("soc: qcom: ipa: GSI transactions")
> Reviewed-by: Mark Bloch <mbloch@...dia.com>
> Signed-off-by: Alex Elder <elder@...aro.org>
> ---
> Note: This was reported via private communication.
> v3: - Added Mark Bloch's reviewed-by tag.
> v2: - Added Bjorn's actual name to tags.  
> 
>  drivers/net/ipa/gsi_trans.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 

Thanks,
Reviewed-by: Leon Romanovsky <leonro@...dia.com>