linux-kernel - 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:   Sat, 8 Aug 2020 07:40:07 +0200
From:   Christoph Hellwig <hch@....de>
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: 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?

> 
> 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---