On 10/25/19 10:27 AM, Jens Axboe wrote: > On 10/25/19 10:21 AM, Pavel Begunkov wrote: >> On 25/10/2019 19:03, Jens Axboe wrote: >>> On 10/25/19 3:55 AM, Pavel Begunkov wrote: >>>> I found 2 problems with __io_sequence_defer(). >>>> >>>> 1. it uses @sq_dropped, but doesn't consider @cq_overflow >>>> 2. @sq_dropped and @cq_overflow are write-shared with userspace, so >>>> it can be maliciously changed. >>>> >>>> see sent liburing test (test/defer *_hung()), which left an unkillable >>>> process for me >>> >>> OK, how about the below. I'll split this in two, as it's really two >>> separate fixes. >> cached_sq_dropped is good, but I was concerned about cached_cq_overflow. >> io_cqring_fill_event() can be called in async, so shouldn't we do some >> synchronisation then? > > We should probably make it an atomic just to be on the safe side, I'll > update the series. Here we go, patch 1: http://git.kernel.dk/cgit/linux-block/commit/?h=for-linus&id=f2a241f596ed9e12b7c8f960e79ccda8053ea294 patch 2: http://git.kernel.dk/cgit/linux-block/commit/?h=for-linus&id=b7d0297d2df5bfa0d1ecf9d6c66d23676751ef6a -- Jens Axboe
