On 5/18/22 09:39, Lee Jones wrote: > 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. I do have kasan enabled. What's fuzzing? -- Jens Axboe
