linux-kernel - Re: [qemu] boot failed: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000

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Date:   Mon, 6 Jul 2020 23:06:58 +0530
From:   Naresh Kamboju <naresh.kamboju@...aro.org>
To:     Dave Jiang <dave.jiang@...el.com>, Arnd Bergmann <arnd@...db.de>,
        Vinod Koul <vkoul@...nel.org>
Cc:     linux-serial@...r.kernel.org,
        open list <linux-kernel@...r.kernel.org>,
        Jiri Slaby <jslaby@...e.com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>, jirislaby@...nel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        ldewangan@...dia.com, Thierry Reding <thierry.reding@...il.com>,
        Jon Hunter <jonathanh@...dia.com>, Qian Cai <cai@....pw>,
        lkft-triage@...ts.linaro.org
Subject: Re: [qemu] boot failed: Unable to handle kernel NULL pointer
 dereference at virtual address 0000000000000000

> Arnd,
> I'm looking at the pl001_dma_probe(), I think we could make it more robust if it
> uses IS_ERR_OR_NULL(chan) instead of IS_ERR(). Should I send a patch for it? I
> suppose looking at the comment header for dma_request_chan() it does say return
> chan ptr or error ptr. Sorry I missed that.
>
>
> Vinod,
> It looks like the only fix for dmaengine for the patch is where Arnd pointed out
> as far as I can tell after auditing it. Let me know how you want to handle this.
> Thanks!

This proposed fix patch applied on top of linux next ( 20200706 tag )
and boot test PASS.

The reported problem got fixed.

Reported-by: Naresh Kamboju <naresh.kamboju@...aro.org>
Tested-by: Naresh Kamboju <naresh.kamboju@...aro.org>

>
> diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
> index 0d6529eff66f..48e159e83cf5 100644
> --- a/drivers/dma/dmaengine.c
> +++ b/drivers/dma/dmaengine.c
> @@ -852,7 +852,7 @@ struct dma_chan *dma_request_chan(struct device *dev, const
> char *name)
>          mutex_lock(&dma_list_mutex);
>          if (list_empty(&dma_device_list)) {
>                  mutex_unlock(&dma_list_mutex);
> -               return NULL;
> +               return ERR_PTR(-ENODEV);
>          }
>
>          list_for_each_entry_safe(d, _d, &dma_device_list, global_node) {

ref:
https://lkft.validation.linaro.org/scheduler/job/1542630#L510

-- 
Linaro LKFT
https://lkft.linaro.org