Re: [PATCH] f2fs: read page index before freeing

[Chao Yu]

On 2018/11/26 18:28, PanBian wrote:
> On Mon, Nov 26, 2018 at 05:13:53PM +0800, Chao Yu wrote:
>> Hi Pan,
>>
>> On 2018/11/22 18:58, Pan Bian wrote:
>>> The function truncate_node frees the page with f2fs_put_page. However,
>>> the page index is read after that. So, the patch reads the index before
>>> freeing the page.
>>
>> I notice that you found another use-after-free bug in ext4, out of
>> curiosity, I'd like to ask how do you find those bugs? by tool or code review?
> 
> I found such bugs by the aid of a tool I wrote recently. I designed a method 
> to automatically find paired alloc/free functions. With such functions, I
> wrote two checkers, one to check mismatched alloc/free bugs, the other to
> check use-after-free and double-free bugs.

Excellent! Do you have any plan to open its source or announce it w/ binary
to linux kernel developers, I think w/ it we can help to improve kernel's
code quality efficiently.

Thanks,

> 
> Best regards,
> Pan Bian
> 
> 
> .
>