Re: BISECT result: 6.0.0-RC kernels trigger Firefox snap bug with 6.0.0-rc3 through 6.0.0-rc7

[Bagas Sanjaya]

On 10/18/22 14:23, Bagas Sanjaya wrote:
> On 10/18/22 09:15, Jintao Yin wrote:
>> Hi Phillip,
>>   There is a logical bug in commit 8fc78b6fe24c36b151ac98d7546591ed92083d4f
>>   which is parent commit of commit b09a7a036d2035b14636cd4c4c69518d73770f65.
>>   
>>   In function squashfs_readahead(...),
>>   file_end is initialized with i_size_read(inode) >> msblk->block_log,
>>   which means the last block index of the file.
>>   But later in the logic to check if the page is last one or not the
>>   code is 
>>     if (pages[nr_pages - 1]->index == file_end && bytes) {
>>       ...
>>     }
>>   , use file_end as the last page index of file but actually is the last
>>   block index, so for the common setup of page and block size, the first 
>>   comparison is true only when pages[nr_pages - 1]->index is 0.
>>   Otherwise, the trailing bytes of last page won't be zeroed.
>>
>>   Maybe it's the real cause of the snap bug in some way.
>>
> 
> Hi Jintao, thanks for explaining the real culprit. However, I'd like to
> see the fixup patch from you so that we can test.
> 

Sorry for inconvenience. Hsin-Yi Wang have already submitted the candidate
fix at [1]. Thanks anyway.

[1]: https://lore.kernel.org/lkml/CAJMQK-hgQEkhgpO9VFOCgn-cKtVsr7Hb_58pAYiGoDi5SzGZtA@xxxxxxxxxxxxxx/

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