On 11/8/21 8:29 AM, Pavel Begunkov wrote: > On 11/3/21 17:01, Lee Jones wrote: >> Good afternoon Pavel, >> >>> syzbot has tested the proposed patch and the reproducer did not trigger any issue: >>> >>> Reported-and-tested-by: syzbot+9671693590ef5aad8953@xxxxxxxxxxxxxxxxxxxxxxxxx >>> >>> Tested on: >>> >>> commit: bff2c168 io_uring: don't retry with truncated iter >>> git tree: https://github.com/isilence/linux.git truncate >>> kernel config: https://syzkaller.appspot.com/x/.config?x=730106bfb5bf8ace >>> dashboard link: https://syzkaller.appspot.com/bug?extid=9671693590ef5aad8953 >>> compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1 >>> >>> Note: testing is done by a robot and is best-effort only. >> >> As you can see in the 'dashboard link' above this bug also affects >> android-5-10 which is currently based on v5.10.75. >> >> I see that the back-port of this patch failed in v5.10.y: >> >> https://lore.kernel.org/stable/163152589512611@xxxxxxxxx/ >> >> And after solving the build-error by back-porting both: >> >> 2112ff5ce0c11 iov_iter: track truncated size >> 89c2b3b749182 io_uring: reexpand under-reexpanded iters >> >> I now see execution tripping the WARN() in iov_iter_revert(): >> >> if (WARN_ON(unroll > MAX_RW_COUNT)) >> return >> >> Am I missing any additional patches required to fix stable/v5.10.y? > > Is it the same syz test? There was a couple more patches for > IORING_SETUP_IOPOLL, but strange if that's not the case. > > > fwiw, Jens decided to replace it with another mechanism shortly > after, so it may be a better idea to backport those. Jens, > what do you think? > > > commit 8fb0f47a9d7acf620d0fd97831b69da9bc5e22ed > Author: Jens Axboe <axboe@xxxxxxxxx> > Date: Fri Sep 10 11:18:36 2021 -0600 > > iov_iter: add helper to save iov_iter state > > commit cd65869512ab5668a5d16f789bc4da1319c435c4 > Author: Jens Axboe <axboe@xxxxxxxxx> > Date: Fri Sep 10 11:19:14 2021 -0600 > > io_uring: use iov_iter state save/restore helpers Yes, I think backporting based on the save/restore setup is the sanest way by far. -- Jens Axboe
