On 8/12/21 2:40 PM, Pavel Begunkov wrote:

For the bug description see 2/2. 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 it has been justly fully reverted

Al, what do you think of this approach? It'll fix the issue, but might be
cleaner to have iov->truncated actually track the truncated size. That'd
make it a more complete solution, at the expense of bloat iov_iter which
this version will not.

-- 
Jens Axboe