Re: [PATCH 2/2] btrfs: fix vanished compression property after failed set

[Nikolay Borisov <nborisov@suse.com>]

On 13.03.19 г. 9:20 ч., Nikolay Borisov wrote:
> 
> 
> On 13.03.19 г. 7:36 ч., Anand Jain wrote:
>> The compression property resets to NULL, instead of the old value if we
>> fail to set the new compression parameter.
>>
>> btrfs prop get /btrfs compression
>>   compression=lzo
>> btrfs prop set /btrfs compression zli
>>   ERROR: failed to set compression for /btrfs: Invalid argument
>> btrfs prop get /btrfs compression
>>
>> This is because the compression property ->validate() is successful for
>> 'zli' as the strncmp() used the len passed from the userland.
>>
>> Fix it by using the expected string length in strncmp().
>>
>> Signed-off-by: Anand Jain <anand.jain@oracle.com>
>> ---
>>  fs/btrfs/props.c | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/btrfs/props.c b/fs/btrfs/props.c
>> index ef6502a94712..7aa362c2fbcf 100644
>> --- a/fs/btrfs/props.c
>> +++ b/fs/btrfs/props.c
>> @@ -277,11 +277,11 @@ static int prop_compression_validate(struct inode *inode, const char *value,
>>  	if (!value)
>>  		return 0;
>>  
>> -	if (!strncmp("lzo", value, len))
>> +	if (!strncmp("lzo", value, 3))
>>  		return 0;
>> -	else if (!strncmp("zlib", value, len))
>> +	else if (!strncmp("zlib", value, 4))
>>  		return 0;
>> -	else if (!strncmp("zstd", value, len))
>> +	else if (!strncmp("zstd", value, 4))
>>  		return 0;
> 
> This also makes the len argument to prop_compression_validate redundant
> and should be removed as well.


As a matter of fact I don't see any value in prop_compression_validate
since the exact same code is used in prop_compression_apply and einval
will be returned if an invalid value is passed in.

> 
>>  
>>  	return -EINVAL;
>>
>