linux-kernel - Re: [PATCH][next] reset: npcm: check for NULL return from syscon_regmap_lookup_by

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Date:   Thu, 14 Nov 2019 13:36:19 +0000
From:   Colin Ian King <colin.king@...onical.com>
To:     Philipp Zabel <p.zabel@...gutronix.de>,
        Avi Fishman <avifishman70@...il.com>,
        Tomer Maimon <tmaimon77@...il.com>,
        Tali Perry <tali.perry1@...il.com>,
        Patrick Venture <venture@...gle.com>,
        Nancy Yuen <yuenn@...gle.com>,
        Benjamin Fair <benjaminfair@...gle.com>,
        openbmc@...ts.ozlabs.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] reset: npcm: check for NULL return from
 syscon_regmap_lookup_by_compat

On 14/11/2019 13:22, Philipp Zabel wrote:
> Hi Colin,
> 
> On Fri, 2019-11-08 at 15:55 +0000, Colin King wrote:
>> From: Colin Ian King <colin.king@...onical.com>
>>
>> Function syscon_regmap_lookup_by_compat can return a NULL pointer, so
> 
> Could you point out where that NULL pointer would come from? As far as I
> understand, syscon_regmap_lookup_by_compatible() should either return a
> negative error code, or syscon->regmap, which should never be NULL.

Maybe I was over-zealous here with the results from the static analyzer.
Re-reading the call chain it does seem like I was mistaken. So NAK this
patch.

Apologies for the noise.

> 
>> the IS_ERR check on the return is incorrect. Fix this by checking for
>> IS_ERR_OR_NULL and return -ENODEV if true.  This avoids a null pointer
>> dereference on gcr_regmap later on.
>>
>> Addresses-Coverity: ("Dereference null return (stat)")
>> Fixes: b3f1d036f26d ("reset: npcm: add NPCM reset controller driver")
>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
>> ---
>>  drivers/reset/reset-npcm.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/reset/reset-npcm.c b/drivers/reset/reset-npcm.c
>> index 2ea4d3136e15..9febf8bed2f6 100644
>> --- a/drivers/reset/reset-npcm.c
>> +++ b/drivers/reset/reset-npcm.c
>> @@ -161,9 +161,9 @@ static int npcm_usb_reset(struct platform_device *pdev, struct npcm_rc_data *rc)
>>  	of_match_device(dev->driver->of_match_table, dev)->data;
>>  
>>  	gcr_regmap = syscon_regmap_lookup_by_compatible(gcr_dt);
>> -	if (IS_ERR(gcr_regmap)) {
>> +	if (IS_ERR_OR_NULL(gcr_regmap)) {
>>  		dev_err(&pdev->dev, "Failed to find %s\n", gcr_dt);
>> -		return PTR_ERR(gcr_regmap);
>> +		return -ENODEV;
>>  	}
>>  
>>  	/* checking which USB device is enabled */
> 
> regards
> Philipp
>