Re: [syzbot] KASAN: use-after-free Read in copy_page_from_iter_atomic (2)

Qu Wenruo
2022-06-15T21:27:45Z

On 2022/6/15 21:21, Christoph Hellwig wrote:
> On Tue, Jun 14, 2022 at 04:50:22PM +0800, Qu Wenruo wrote:
>> The same way as data?
>>
>> map-logical to find the location of a mirror, write 4 bytes of zero into
>> the location, then call it a day.
>>
>> Although for metadata, you may want to choose a metadata that would
>> definitely get read.
>> Thus tree root is a good candidate.
>
> And how do I find out the logic address of the tree root?

For tree root, "btrfs ins dump-super <dev> | grep '^root\s'.

For other tree blocks, "btrfs ins dump-tree <dev>" then with other other
keywords to grab.

Thanks,
Qu