On 3/21/20 6:38 AM, Hillf Danton wrote: > > On Fri, 20 Mar 2020 22:50:12 -0700 >> syzbot found the following crash on: >> >> HEAD commit: cd607737 Merge tag '5.6-rc6-smb3-fixes' of git://git.samba.. >> git tree: upstream >> console output: https://syzkaller.appspot.com/x/log.txt?x=1730c023e00000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=9f894bd92023de02 >> dashboard link: https://syzkaller.appspot.com/bug?extid=538d1957ce178382a394 >> compiler: gcc (GCC) 9.0.0 20181231 (experimental) >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=108ebbe3e00000 >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=139fb973e00000 >> >> The bug was bisected to: >> >> commit 05f3fb3c5397524feae2e73ee8e150a9090a7da2 >> Author: Jens Axboe <axboe@xxxxxxxxx> >> Date: Mon Dec 9 18:22:50 2019 +0000 >> >> io_uring: avoid ring quiesce for fixed file set unregister and update >> >> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1237ad73e00000 >> final crash: https://syzkaller.appspot.com/x/report.txt?x=1137ad73e00000 >> console output: https://syzkaller.appspot.com/x/log.txt?x=1637ad73e00000 >> >> IMPORTANT: if you fix the bug, please add the following tag to the commit: >> Reported-by: syzbot+538d1957ce178382a394@xxxxxxxxxxxxxxxxxxxxxxxxx >> Fixes: 05f3fb3c5397 ("io_uring: avoid ring quiesce for fixed file set unregister and update") >> >> INFO: task syz-executor975:9880 blocked for more than 143 seconds. >> Not tainted 5.6.0-rc6-syzkaller #0 >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> syz-executor975 D27576 9880 9878 0x80004000 >> Call Trace: >> schedule+0xd0/0x2a0 kernel/sched/core.c:4154 >> schedule_timeout+0x6db/0xba0 kernel/time/timer.c:1871 >> do_wait_for_common kernel/sched/completion.c:83 [inline] >> __wait_for_common kernel/sched/completion.c:104 [inline] >> wait_for_common kernel/sched/completion.c:115 [inline] >> wait_for_completion+0x26a/0x3c0 kernel/sched/completion.c:136 >> io_queue_file_removal+0x1af/0x1e0 fs/io_uring.c:5826 >> __io_sqe_files_update.isra.0+0x3a1/0xb00 fs/io_uring.c:5867 >> io_sqe_files_update fs/io_uring.c:5918 [inline] >> __io_uring_register+0x377/0x2c00 fs/io_uring.c:7131 >> __do_sys_io_uring_register fs/io_uring.c:7202 [inline] >> __se_sys_io_uring_register fs/io_uring.c:7184 [inline] >> __x64_sys_io_uring_register+0x192/0x560 fs/io_uring.c:7184 >> do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294 >> entry_SYSCALL_64_after_hwframe+0x49/0xbe >> RIP: 0033:0x440659 >> Code: Bad RIP value. >> RSP: 002b:00007ffc4689a358 EFLAGS: 00000246 ORIG_RAX: 00000000000001ab >> RAX: ffffffffffffffda RBX: 00007ffc4689a360 RCX: 0000000000440659 >> RDX: 0000000020000300 RSI: 0000000000000006 RDI: 0000000000000003 >> RBP: 0000000000000005 R08: 0000000000000001 R09: 00007ffc46890031 >> R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000401f40 >> R13: 0000000000401fd0 R14: 0000000000000000 R15: 0000000000000000 >> >> Showing all locks held in the system: >> 1 lock held by khungtaskd/1137: >> #0: ffffffff897accc0 (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:5331 >> 1 lock held by rsyslogd/9761: >> #0: ffff8880a8f3ada0 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xe3/0x100 fs/file.c:821 >> 2 locks held by getty/9850: >> #0: ffff88809fad3090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 >> #1: ffffc900017bb2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x21d/0x1b30 drivers/tty/n_tty.c:2156 >> 2 locks held by getty/9851: >> #0: ffff8880a7b96090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 >> #1: ffffc900017cb2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x21d/0x1b30 drivers/tty/n_tty.c:2156 >> 2 locks held by getty/9852: >> #0: ffff88809e41c090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 >> #1: ffffc900017eb2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x21d/0x1b30 drivers/tty/n_tty.c:2156 >> 2 locks held by getty/9853: >> #0: ffff888090392090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 >> #1: ffffc900017ab2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x21d/0x1b30 drivers/tty/n_tty.c:2156 >> 2 locks held by getty/9854: >> #0: ffff88809fb1b090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 >> #1: ffffc900017db2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x21d/0x1b30 drivers/tty/n_tty.c:2156 >> 2 locks held by getty/9855: >> #0: ffff88809a302090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 >> #1: ffffc9000178b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x21d/0x1b30 drivers/tty/n_tty.c:2156 >> 2 locks held by getty/9856: >> #0: ffff88809d9dc090 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:267 >> #1: ffffc9000172b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x21d/0x1b30 drivers/tty/n_tty.c:2156 >> 1 lock held by syz-executor975/9880: >> #0: ffff88808f392320 (&ctx->uring_lock){+.+.}, at: __do_sys_io_uring_register fs/io_uring.c:7201 [inline] >> #0: ffff88808f392320 (&ctx->uring_lock){+.+.}, at: __se_sys_io_uring_register fs/io_uring.c:7184 [inline] >> #0: ffff88808f392320 (&ctx->uring_lock){+.+.}, at: __x64_sys_io_uring_register+0x181/0x560 fs/io_uring.c:7184 >> >> ============================================= >> >> NMI backtrace for cpu 1 >> CPU: 1 PID: 1137 Comm: khungtaskd Not tainted 5.6.0-rc6-syzkaller #0 >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 >> Call Trace: >> __dump_stack lib/dump_stack.c:77 [inline] >> dump_stack+0x188/0x20d lib/dump_stack.c:118 >> nmi_cpu_backtrace.cold+0x70/0xb1 lib/nmi_backtrace.c:101 >> nmi_trigger_cpumask_backtrace+0x231/0x27e lib/nmi_backtrace.c:62 >> trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] >> check_hung_uninterruptible_tasks kernel/hung_task.c:205 [inline] >> watchdog+0xa8c/0x1010 kernel/hung_task.c:289 >> kthread+0x357/0x430 kernel/kthread.c:255 >> ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 >> Sending NMI from CPU 1 to CPUs 0: >> NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60 > > Flush work before waiting for completion. > > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -5823,8 +5823,8 @@ static bool io_queue_file_removal(struct > > if (pfile == &pfile_stack) { > percpu_ref_switch_to_atomic(&data->refs, io_atomic_switch); > - wait_for_completion(&done); > flush_work(&data->ref_work); > + wait_for_completion(&done); > return false; > } > > -- > > And perhaps a tiny cleanup: no deed to wait for completion as > flushing work itself will wait until the work is done. Care to send this version as a real patch? Seems kind of pointless to just do the above change with that in mind. And then at the same time turn ->done into ->do_file_put or something, and make it a bool. -- Jens Axboe
