On Wed, 18 May 2022, Jens Axboe wrote: > On 5/18/22 9:14 AM, Lee Jones wrote: > > On Wed, 18 May 2022, Jens Axboe wrote: > > > >> On 5/18/22 6:54 AM, Jens Axboe wrote: > >>> On 5/18/22 6:52 AM, Jens Axboe wrote: > >>>> On 5/18/22 6:50 AM, Lee Jones wrote: > >>>>> On Tue, 17 May 2022, Jens Axboe wrote: > >>>>> > >>>>>> On 5/17/22 7:00 AM, Lee Jones wrote: > >>>>>>> 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. > >>>>>> > >>>>>> Can you see if this helps? Untested... > >>>>> > >>>>> What base does this apply against please? > >>>>> > >>>>> I tried Mainline and v5.10.116 and both failed. > >>>> > >>>> It's against 5.10.116, so that's puzzling. Let me double check I sent > >>>> the right one... > >>> > >>> Looks like I sent the one from the wrong directory, sorry about that. > >>> This one should be better: > >> > >> Nope, both are the right one. Maybe your mailer is mangling the patch? > >> I'll attach it gzip'ed here in case that helps. > > > > Okay, that applied, thanks. > > > > Unfortunately, I am still able to crash the kernel in the same way. > > Alright, maybe it's not enough. I can't get your reproducer to crash, > unfortunately. I'll try on a different box. You need to have fuzzing and kasan enabled. Here's the .config I'm using: https://termbin.com/3lvp Pop the invocation in a while loop: while true; do ./repro; done This has a 100% success rate for me. -- Lee Jones [李琼斯] Principal Technical Lead - Developer Services Linaro.org │ Open source software for Arm SoCs Follow Linaro: Facebook | Twitter | Blog
