Re: [PATCH] mmc: pxamci: Fix passing NULL to PTR_ERR() in pxamci_probe()

Khalid Aziz
2025-10-09T15:53:05Z

On 10/9/25 2:57 AM, Uwe Kleine-König wrote:
> On Tue, Oct 07, 2025 at 09:47:44PM +0530, Rakuram Eswaran wrote:
>> Smatch reported:
>> drivers/mmc/host/pxamci.c:709 pxamci_probe() warn: passing zero to 'PTR_ERR'
>>
>> Case 1:
>> When dma_request_chan() fails, host->dma_chan_rx is an ERR_PTR(),
>> but it is reset to NULL before using PTR_ERR(), resulting in PTR_ERR(0).
>> This mistakenly returns 0 instead of the real error code.
>>
>> Case 2:
>> When devm_clk_get() fails, host->clk is an ERR_PTR() resulting in the similar
>> issue like case 1.
>>
>> Store the error code before nullifying the pointers in both the cases.
>
> Why is the pointer set to NULL at all? This is in both cases memory that
> is freed directly afterwards (as `host` is devm managed). So I'd claim

I am not sure that sounds right. Looking at the code for
__devm_clk_get(), if devres_alloc() fails, it returns -ENOMEM. If any of
the other steps after a successful devres_alloc() fail, code goes
through possibly clk_put() if needed and then devres_free(). So the
resources are already freed at this point before the return to
pxamci_probe(). The only thing left to do is to set host->clk to NULL
since it would be set to an error pointer at this point.

Am I missing something?

Thanks,
Khalid

>
> diff --git a/drivers/mmc/host/pxamci.c b/drivers/mmc/host/pxamci.c
> index 26d03352af63..404f78198252 100644
> --- a/drivers/mmc/host/pxamci.c
> +++ b/drivers/mmc/host/pxamci.c
> @@ -652,10 +652,8 @@ static int pxamci_probe(struct platform_device *pdev)
> host->clkrt = CLKRT_OFF;
>
> host->clk = devm_clk_get(dev, NULL);
> - if (IS_ERR(host->clk)) {
> - host->clk = NULL;
> + if (IS_ERR(host->clk))
> return PTR_ERR(host->clk);
> - }
>
> host->clkrate = clk_get_rate(host->clk);
>
> @@ -704,11 +702,9 @@ static int pxamci_probe(struct platform_device *pdev)
> platform_set_drvdata(pdev, mmc);
>
> host->dma_chan_rx = dma_request_chan(dev, "rx");
> - if (IS_ERR(host->dma_chan_rx)) {
> - host->dma_chan_rx = NULL;
> + if (IS_ERR(host->dma_chan_rx))
> return dev_err_probe(dev, PTR_ERR(host->dma_chan_rx),
> "unable to request rx dma channel\n");
> - }
>
> host->dma_chan_tx = dma_request_chan(dev, "tx");
> if (IS_ERR(host->dma_chan_tx)) {
>
> is a superior patch.
>
> Best regards
> Uwe