Re: [bug report] btrfs: change set_level() to bound the level passed in

[David Sterba <dsterba@suse.cz>]

On Thu, Feb 07, 2019 at 01:36:47PM +0300, Dan Carpenter wrote:
> Hello Dennis Zhou,
> 
> The patch a67dc67a2cb8: "btrfs: change set_level() to bound the level
> passed in" from Jan 28, 2019, leads to the following static checker
> warning:
> 
> 	fs/btrfs/compression.c:1576 btrfs_compress_str2level()
> 	error: uninitialized symbol 'level'.
> 
> fs/btrfs/compression.c
>     1566 unsigned int btrfs_compress_str2level(unsigned int type, const char *str)
>     1567 {
>     1568 	unsigned int level;
>     1569 	int ret;
>     1570 
>     1571 	if (!type)
>     1572 		return 0;
>     1573 
>     1574 	if (str[0] == ':') {
>     1575 		ret = kstrtouint(str + 1, 10, &level);
> --> 1576 		if (ret)
>     1577 			level = 0;
> 
> I feel like if the user gives bad input then we should just return an
> error code instead of picking a level.

We've debated a bit and a warning with fallback to default is the
preferred option.
> 
>     1578 	}
> 
> level is not initialized if the first character is not ':'.

Right that's a bug, can be fixed by initializing level to 0, the
set_level() implementations will fall back to default then.

Thanks for the report.

> 
>     1579 
>     1580 	level = btrfs_compress_op[type]->set_level(level);
>     1581 
>     1582 	return level;
>     1583 }