linux-kernel - Re: drivers/memory/tegra/tegra186.c:74:49: warning: '%u' directive output may be truncated writing between 1 and 10 bytes into a region of size 6

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Message-ID: <a97fb789-ce3f-44bc-ab0c-797d18cd2cc3@nvidia.com>
Date:   Wed, 25 Oct 2023 11:54:54 +0530
From:   Ashish Mhetre <amhetre@...dia.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>,
        kernel test robot <lkp@...el.com>
Cc:     oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Dmitry Osipenko <dmitry.osipenko@...labora.com>,
        Thierry Reding <treding@...dia.com>
Subject: Re: drivers/memory/tegra/tegra186.c:74:49: warning: '%u' directive
 output may be truncated writing between 1 and 10 bytes into a region of size
 6


On 10/19/2023 7:06 PM, Krzysztof Kozlowski wrote:
> External email: Use caution opening links or attachments
>
>
> On 18/10/2023 14:32, kernel test robot wrote:
>> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>> head:   06dc10eae55b5ceabfef287a7e5f16ceea204aa0
>> commit: a7cffa11fa9232eabf0c4f441dc53002978ab526 memory: tegra: Add memory controller channels support
>> date:   1 year, 5 months ago
>> config: arm64-randconfig-r036-20230512 (https://download.01.org/0day-ci/archive/20231018/202310182004.0XOYolzI-lkp@intel.com/config)
>> compiler: aarch64-linux-gcc (GCC) 11.3.0
>> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231018/202310182004.0XOYolzI-lkp@intel.com/reproduce)
>>
>> If you fix the issue in a separate patch/commit (i.e. not just a new version of
>> the same patch/commit), kindly add following tags
>> | Reported-by: kernel test robot <lkp@...el.com>
>> | Closes: https://lore.kernel.org/oe-kbuild-all/202310182004.0XOYolzI-lkp@intel.com/
>>
>> All warnings (new ones prefixed by >>):
> Ashish,
>
> Are you planning to respond to this?
>
> Best regards,
> Krzysztof

Hi Krzysztof,

The value of mc->soc->num_channels is not more that 16. The number of
characters written in 'name' variable won't be more than 4 which is less
than buffer size of 8 bytes. So, can we ignore this warning?
If not, then I can fix this with a patch to check the return value of
snprintf and compare that with size of buffer 'name'. Something like:

-               snprintf(name, sizeof(name), "ch%u", i);
+               int n = snprintf(name, sizeof(name), "ch%u", i);
+
+               if (n < 0) {
+                       dev_err(&pdev->dev, "snprintf failed\n");
+                       return -EFAULT;
+               }
+               if ((size_t)n > sizeof(name)) {
+                       dev_err(&pdev->dev, "snprintf output is 
truncated\n");
+                       return -EFAULT;
+               }

Thanks,

Ashish Mhetre