Re: [PATCH v3 0/2] iter revert problems

From: Jens Axboe
Date: Fri Sep 03 2021 - 20:57:38 EST

On 9/3/21 3:55 PM, Al Viro wrote:
> On Fri, Sep 03, 2021 at 02:55:26PM -0600, Jens Axboe wrote:
>> On 8/23/21 4:18 AM, Pavel Begunkov wrote:
>>> iov_iter_revert() doesn't go well with iov_iter_truncate() in all
>>> cases, see 2/2 for the bug description. As mentioned there the current
>>> problems is because of generic_write_checks(), but there was also a
>>> similar case fixed in 5.12, which should have been triggerable by normal
>>> write(2)/read(2) and others.
>>> It may be better to enforce reexpands as a long term solution, but for
>>> now this patchset is quickier and easier to backport.
>>> v2: don't fail if it was justly fully reverted
>>> v3: use truncated size + reexapand based approach
>> Al, let's get this upstream. How do you want to handle it? I can take
>> it through the io_uring tree, or it can go through your tree. I really
>> don't care which route it takes, but we should get this upstream as
>> it solves a real problem.
> Grabbed, will test and send a pull request...

Thanks Al! We should mark these for stable as well.

Jens Axboe