linux-kernel - RE: [kbuild-all] Re: fs/init.c:72:8: warning: Variable 'error' is reassigned a value before the old one has been used.

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Date:   Mon, 10 Aug 2020 09:28:27 +0000
From:   "Xia, Hui" <hui.xia@...el.com>
To:     Christoph Hellwig <hch@....de>, lkp <lkp@...el.com>
CC:     "kbuild-all@...ts.01.org" <kbuild-all@...ts.01.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>
Subject: RE: [kbuild-all] Re: fs/init.c:72:8: warning: Variable 'error' is
 reassigned a value before the old one has been used.



>-----Original Message-----
>From: Christoph Hellwig <hch@....de>
>Sent: 2020年8月8日 13:40
>To: kernel test robot <lkp@...el.com>
>Cc: Christoph Hellwig <hch@....de>; kbuild-all@...ts.01.org; linux-
>kernel@...r.kernel.org; viro@...iv.linux.org.uk
>Subject: [kbuild-all] Re: fs/init.c:72:8: warning: Variable 'error' is reassigned a
>value before the old one has been used.
>
>On Sat, Aug 08, 2020 at 11:35:45AM +0800, kernel test robot wrote:
>> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>> head:   30185b69a2d533c4ba6ca926b8390ce7de495e29
>> commit: 4b7ca5014cbef51cdb99fd644eae4f3773747a05 init: add an init_chroot
>helper
>> date:   8 days ago
>> compiler: hppa-linux-gcc (GCC) 9.3.0
>>
>> If you fix the issue, kindly add following tag as appropriate
>> Reported-by: kernel test robot <lkp@...el.com>
>>
>>
>> cppcheck warnings: (new ones prefixed by >>)
>>
>> >> fs/init.c:72:8: warning: Variable 'error' is reassigned a value
>> >> before the old one has been used. [redundantAssignment]
>>     error = security_path_chroot(&path);
>>           ^
>>    fs/init.c:69:8: note: Variable 'error' is reassigned a value before the old one
>has been used.
>>     error = -EPERM;
>>           ^
>>    fs/init.c:72:8: note: Variable 'error' is reassigned a value before the old one
>has been used.
>>     error = security_path_chroot(&path);
>
>I really don't understand the warning.  We assign a value to error, if there is an
>error we jump the out labe and return it, or else continue.
>
>That is a pretty common pattern in the kernel.  What do I miss?

Please ignore this report. It is false positive.
We will double check this type of warning in future. Sorry for inconvenient.

Thanks,
Hui
>
>>
>> vim +/error +72 fs/init.c
>>
>>     57
>>     58	int __init init_chroot(const char *filename)
>>     59	{
>>     60		struct path path;
>>     61		int error;
>>     62
>>     63		error = kern_path(filename, LOOKUP_FOLLOW |
>LOOKUP_DIRECTORY, &path);
>>     64		if (error)
>>     65			return error;
>>     66		error = inode_permission(path.dentry->d_inode, MAY_EXEC |
>MAY_CHDIR);
>>     67		if (error)
>>     68			goto dput_and_out;
>>     69		error = -EPERM;
>>     70		if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
>>     71			goto dput_and_out;
>>   > 72		error = security_path_chroot(&path);
>>     73		if (error)
>>     74			goto dput_and_out;
>>     75		set_fs_root(current->fs, &path);
>>     76	dput_and_out:
>>     77		path_put(&path);
>>     78		return error;
>>     79	}
>>     80
>>
>> ---
>> 0-DAY CI Kernel Test Service, Intel Corporation
>> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
>---end quoted text---
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