[PATCH] erofs-utils: lib: reset hc to avoid 32-bit overflow of kite-deflate

[Gao Xiang]

On 2024/1/24 18:40, Yifan Zhao wrote:
> 
> On 2024/1/24 17:53, Gao Xiang wrote:
>> Hi Yifan,
>>
>> On 2024/1/24 17:47, Yifan Zhao wrote:
>>>
>>> On 1/24/24 17:16, Gao Xiang wrote:
>>>> Yifan reported a "segmentation fault (core dumped)" error days ago
>>>> with a large dataset (enwik9 x 5).   Let's fix it.
>>>>
>>>> Reported-by: Yifan Zhao <zhaoyifan at sjtu.edu.cn>
>>>> Fixes: 861037f4fc15 ("erofs-utils: add a built-in DEFLATE compressor")
>>>> Signed-off-by: Gao Xiang <hsiangkao at linux.alibaba.com>
>>>> ---
>>>>   include/erofs/defs.h |  3 +++
>>>>   lib/kite_deflate.c   | 12 ++++++++++++
>>>>   2 files changed, 15 insertions(+)
>>>>
>>>> diff --git a/include/erofs/defs.h b/include/erofs/defs.h
>>>> index e7384a1..4ea9a55 100644
>>>> --- a/include/erofs/defs.h
>>>> +++ b/include/erofs/defs.h
>>>> @@ -343,6 +343,9 @@ unsigned long __roundup_pow_of_two(unsigned long n)
>>>>   #define ST_MTIM_NSEC(stbuf) 0
>>>>   #endif
>>>> +#define likely(x)      __builtin_expect(!!(x), 1)
>>>> +#define unlikely(x)    __builtin_expect(!!(x), 0)
>>>> +
>>>>   #ifdef __cplusplus
>>>>   }
>>>>   #endif
>>>> diff --git a/lib/kite_deflate.c b/lib/kite_deflate.c
>>>> index 8667954..cb81626 100644
>>>> --- a/lib/kite_deflate.c
>>>> +++ b/lib/kite_deflate.c
>>>> @@ -859,6 +859,18 @@ static void kite_mf_reset(struct kite_matchfinder *mf,
>>>>        */
>>>>       mf->base += mf->offset + kHistorySize32 + 1;
>>>> +    /*
>>>> +     * Unlike other LZ encoders like liblzma [1], we simply reset the hash
>>>> +     * chain instead of normalization.  This avoids extra complexity, as we
>>>> +     * don't consider extreme large input buffers in one go.
>>>> +     *
>>>> +     * [1] https://github.com/tukaani-project/xz/blob/v5.4.0/src/liblzma/lz/lz_encoder_mf.c#L94
>>>> +     */
>>>> +    if (unlikely(mf->base > ((typeof(mf->base))-1) >> 1)) {
>>>> +        mf->base = kHistorySize32 + 1;
>>>> +        memset(mf->hash, 0, 0x10000 * sizeof(mf->hash[0]));
>>>> +        memset(mf->chain, 0, sizeof(mf->chain[0]) * mf->wsiz);
>>
>> This line
>>
>> memset(mf->chain, 0, sizeof(mf->chain[0]) * mf->wsiz);
>>
>> is also unnecessary, let me remove it when applying.
>>
>> I think it still works on your side.
>>
>>
>>>> +    }
>>>>       mf->offset = 0;
>>>>       mf->cyclic_pos = 0;
>>>
>>> Tested-by: Yifan Zhao <zhaoyifan at sjtu.edu.cn>
>>
>> Thanks!
>>
>> Thanks,
>> Gao Xiang
>>
>>>
>>>
>>> Yifan Zhao
>>>
>>> Thanks
> 
> 
> Yes, it still works for me.
> 
> Tested-by: Yifan Zhao <zhaoyifan at sjtu.edu.cn>

Applied, thanks!

Thanks,
Gao Xiang

> 
> 
> Thanks,
> 
> Yifan Zhao