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). -- Lee Jones [李琼斯] Principal Technical Lead - Developer Services Linaro.org │ Open source software for Arm SoCs Follow Linaro: Facebook | Twitter | Blog
