Re: [PATCH v2 2/4] btrfs: also validate compression levels in btrfs_compress_is_valid_type()

在 2026/8/9 13:05, koraynilay 写道:
> On Sun Aug 9, 2026 at 4:53 AM CEST, Qu Wenruo wrote:
>> Please make sure every commit compiles, this will easily break bisection.
>>
>> You're changing a function prototype and implementation without
>> modifying any callers, this fails compiling.
> 
> Right, I'm sorry, I didn't notice I changed the caller in 3/4 as that
> call point also had other changes.
> 
>> Furthermore, I do not think it's a good idea to just rely on the strlen().
>>
>> E.g. if a crafted image removing the last terminating NUL, relying
>> strlen() can easily go beyond the expected string.
>>
>> I think the change to remove @len is going to reduce the robustness of
>> the original code.
> 
> That was what I feared too, the problem is that
> btrfs_compress_str2level() uses kstrtoint(), which requires the string
> to be null-terminated[1], so the len paramenter would only be used by
> if (len < comp_len) and that reduces the robustness even more IMO, since
> a developer could think it's safe because of len, while it actually
> isn't because of kstrtoint().
> The only fix I can think of would be to use
> _parse_integer_limit(..., len) directly or write a wrapper.
> Or just document that it needs a null-terminated string.

OK, you're right, in that case we're not losing anything.

So feel free to go ahead just fixing the compiling error.

Thanks,
Qu

> 
> Thanks.
> 
> Best,
> koraynilay
> 
> [1]:
> from lib/kstrtox.c:251:
>   * kstrtoint - convert a string to an int
>   * @s: The start of the string. The string must be null-terminated [...]