linux-kernel - Re: [PATCH 4.19] dmaengine: at

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Message-ID: <80065eac-7dce-aadf-51ef-9a290973b9ec@microchip.com>
Date:   Wed, 23 Sep 2020 08:13:02 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <pavel@....cz>, <linux-kernel@...r.kernel.org>,
        <dmaengine@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <dan.j.williams@...el.com>,
        <vkoul@...nel.org>, <Ludovic.Desroches@...rochip.com>,
        <stable@...r.kernel.org>, <greg@...ah.com>
Subject: Re: [PATCH 4.19] dmaengine: at_hdmac: Fix memory leak

Hi, Pavel,

On 9/20/20 11:28 AM, Pavel Machek wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> This fixes memory leak in at_hdmac. Mainline does not have the same
> problem.
> 
> Signed-off-by: Pavel Machek (CIP) <pavel@...x.de>
> 
> diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
> index 86427f6ba78c..0847b2055857 100644
> --- a/drivers/dma/at_hdmac.c
> +++ b/drivers/dma/at_hdmac.c
> @@ -1714,8 +1714,10 @@ static struct dma_chan *at_dma_xlate(struct of_phandle_args *dma_spec,
>         atslave->dma_dev = &dmac_pdev->dev;
> 
>         chan = dma_request_channel(mask, at_dma_filter, atslave);
> -       if (!chan)
> +       if (!chan) {
> +               kfree(atslave);
>                 return NULL;
> +       }

Thanks for submitting this to stable. While the fix is good, you can instead
cherry-pick the commit that hit upstream. In order to do that cleanly on top
of v4.19.145, you have to pick two other fixes:

commit a6e7f19c9100 ("dmaengine: at_hdmac: Substitute kzalloc with kmalloc")
commit 3832b78b3ec2 ("dmaengine: at_hdmac: add missing put_device() call in at_dma_xlate()")
commit a6e7f19c9100 ("dmaengine: at_hdmac: Substitute kzalloc with kmalloc")

There are also some locking/deadlock fixes in mainline for this driver,
depending on the time you can allocate for this, the list of patches can increase.
I should have Cc'ed stable@...r.kernel.org in the first place, my bad.

Also it may worth to read the rules for submitting to stable at:
https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html

Cheers,
ta