On Tue, 17 May 2022, Jens Axboe wrote: > On 5/17/22 6:36 AM, Lee Jones wrote: > > On Tue, 17 May 2022, Jens Axboe wrote: > > > >> On 5/17/22 6:24 AM, Lee Jones wrote: > >>> On Tue, 17 May 2022, Jens Axboe wrote: > >>> > >>>> On 5/17/22 5:41 AM, Lee Jones wrote: > >>>>> Good afternoon Jens, Pavel, et al., > >>>>> > >>>>> Not sure if you are presently aware, but there appears to be a > >>>>> use-after-free issue affecting the io_uring worker driver (fs/io-wq.c) > >>>>> in Stable v5.10.y. > >>>>> > >>>>> The full sysbot report can be seen below [0]. > >>>>> > >>>>> The C-reproducer has been placed below that [1]. > >>>>> > >>>>> I had great success running this reproducer in an infinite loop. > >>>>> > >>>>> My colleague reverse-bisected the fixing commit to: > >>>>> > >>>>> commit fb3a1f6c745ccd896afadf6e2d6f073e871d38ba > >>>>> Author: Jens Axboe <axboe@xxxxxxxxx> > >>>>> Date: Fri Feb 26 09:47:20 2021 -0700 > >>>>> > >>>>> io-wq: have manager wait for all workers to exit > >>>>> > >>>>> Instead of having to wait separately on workers and manager, just have > >>>>> the manager wait on the workers. We use an atomic_t for the reference > >>>>> here, as we need to start at 0 and allow increment from that. Since the > >>>>> number of workers is naturally capped by the allowed nr of processes, > >>>>> and that uses an int, there is no risk of overflow. > >>>>> > >>>>> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> > >>>>> > >>>>> fs/io-wq.c | 30 ++++++++++++++++++++++-------- > >>>>> 1 file changed, 22 insertions(+), 8 deletions(-) > >>>> > >>>> Does this fix it: > >>>> > >>>> commit 886d0137f104a440d9dfa1d16efc1db06c9a2c02 > >>>> Author: Jens Axboe <axboe@xxxxxxxxx> > >>>> Date: Fri Mar 5 12:59:30 2021 -0700 > >>>> > >>>> io-wq: fix race in freeing 'wq' and worker access > >>>> > >>>> Looks like it didn't make it into 5.10-stable, but we can certainly > >>>> rectify that. > >>> > >>> Thanks for your quick response Jens. > >>> > >>> This patch doesn't apply cleanly to v5.10.y. > >> > >> This is probably why it never made it into 5.10-stable :-/ > > > > Right. It doesn't apply at all unfortunately. > > > >>> I'll have a go at back-porting it. Please bear with me. > >> > >> Let me know if you into issues with that and I can help out. > > > > I think the dependency list is too big. > > > > Too much has changed that was never back-ported. > > > > Actually the list of patches pertaining to fs/io-wq.c alone isn't so > > bad, I did start to back-port them all but some of the big ones have > > fs/io_uring.c changes incorporated and that list is huge (256 patches > > from v5.10 to the fixing patch mentioned above). > > The problem is that 5.12 went to the new worker setup, and this patch > landed after that even though it also applies to the pre-native workers. > Hence the dependency chain isn't really as long as it seems, probably > just a few patches backporting the change references and completions. > > I'll take a look this afternoon. Thanks Jens. I really appreciate it. -- Lee Jones [李琼斯] Principal Technical Lead - Developer Services Linaro.org │ Open source software for Arm SoCs Follow Linaro: Facebook | Twitter | Blog
