linux-kernel - Re: [PATCH] net: stmmac: add sanity check to device_property_read_u32

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Message-ID: <c46d2d17-c35b-46f0-0674-0c55bea3a272@canonical.com>
Date:   Tue, 25 Jun 2019 08:58:10 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     alexandre.torgue@...com, davem@...emloft.net, joabreu@...opsys.com,
        kernel-janitors@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        mcoquelin.stm32@...il.com, netdev@...r.kernel.org,
        peppe.cavallaro@...com
Subject: Re: [PATCH] net: stmmac: add sanity check to
 device_property_read_u32_array call

On 25/06/2019 05:44, Martin Blumenstingl wrote:
> Hi Colin,
> 
> On Thu, Jun 20, 2019 at 3:34 AM Martin Blumenstingl
> <martin.blumenstingl@...glemail.com> wrote:
>>
>> Hi Colin,
>>
>> On Wed, Jun 19, 2019 at 8:55 AM Colin Ian King <colin.king@...onical.com> wrote:
>>>
>>> On 19/06/2019 06:13, Martin Blumenstingl wrote:
>>>> Hi Colin,
>>>>
>>>>> Currently the call to device_property_read_u32_array is not error checked
>>>>> leading to potential garbage values in the delays array that are then used
>>>>> in msleep delays.  Add a sanity check to the property fetching.
>>>>>
>>>>> Addresses-Coverity: ("Uninitialized scalar variable")
>>>>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
>>>> I have also sent a patch [0] to fix initialize the array.
>>>> can you please look at my patch so we can work out which one to use?
>>>>
>>>> my concern is that the "snps,reset-delays-us" property is optional,
>>>> the current dt-bindings documentation states that it's a required
>>>> property. in reality it isn't, there are boards (two examples are
>>>> mentioned in my patch: [0]) without it.
>>>>
>>>> so I believe that the resulting behavior has to be:
>>>> 1. don't delay if this property is missing (instead of delaying for
>>>>    <garbage value> ms)
>>>> 2. don't error out if this property is missing
>>>>
>>>> your patch covers #1, can you please check whether #2 is also covered?
>>>> I tested case #2 when submitting my patch and it worked fine (even
>>>> though I could not reproduce the garbage values which are being read
>>>> on some boards)
> in the meantime I have tested your patch.
> when I don't set the "snps,reset-delays-us" property then I get the
> following error:
>   invalid property snps,reset-delays-us
> 
> my patch has landed in the meantime: [0]
> how should we proceed with your patch?

I'm out of the office today. I'll get back to you on this tomorrow.

Colin
> 
> 
> Martin
> 
> 
> [0] https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/commit/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c?id=84ce4d0f9f55b4f4ca4d4edcbb54a23d9dad1aae
>