On 12/21/19 6:43 AM, Hillf Danton wrote: > > On Sat, 21 Dec 2019 00:05:07 -0800 >> Hello, >> >> syzbot found the following crash on: >> >> HEAD commit: 7ddd09fc Add linux-next specific files for 20191220 >> git tree: linux-next >> console output: https://syzkaller.appspot.com/x/log.txt?x=12a18cc6e00000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=f183b01c3088afc6 >> dashboard link: https://syzkaller.appspot.com/bug?extid=8c4a14856e657b43487c >> compiler: gcc (GCC) 9.0.0 20181231 (experimental) >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14b8f351e00000 >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14b51925e00000 >> >> IMPORTANT: if you fix the bug, please add the following tag to the commit: >> Reported-by: syzbot+8c4a14856e657b43487c@xxxxxxxxxxxxxxxxxxxxxxxxx >> >> ------------[ cut here ]------------ >> WARNING: CPU: 1 PID: 11482 at lib/percpu-refcount.c:111 >> percpu_ref_exit+0xab/0xd0 lib/percpu-refcount.c:111 >> Kernel panic - not syncing: panic_on_warn set ... >> CPU: 1 PID: 11482 Comm: syz-executor051 Not tainted >> 5.5.0-rc2-next-20191220-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+0x197/0x210 lib/dump_stack.c:118 >> panic+0x2e3/0x75c kernel/panic.c:221 >> __warn.cold+0x2f/0x3e kernel/panic.c:582 >> report_bug+0x289/0x300 lib/bug.c:195 >> fixup_bug arch/x86/kernel/traps.c:174 [inline] >> fixup_bug arch/x86/kernel/traps.c:169 [inline] >> do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:267 >> do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:286 >> invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027 >> RIP: 0010:percpu_ref_exit+0xab/0xd0 lib/percpu-refcount.c:111 >> Code: 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 75 1d 48 c7 43 08 03 00 >> 00 00 e8 01 41 e5 fd 5b 41 5c 41 5d 5d c3 e8 f5 40 e5 fd <0f> 0b eb bf 4c >> 89 ef e8 29 2c 23 fe eb d9 e8 82 2b 23 fe eb a7 4c >> RSP: 0018:ffffc9000cb17968 EFLAGS: 00010293 >> RAX: ffff8880a3390640 RBX: ffff8880a83a8010 RCX: ffffffff83901432 >> RDX: 0000000000000000 RSI: ffffffff8390149b RDI: ffff8880a83a8028 >> RBP: ffffc9000cb17980 R08: ffff8880a3390640 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000000 R12: 0000607f51435750 >> R13: ffff8880a83a8018 R14: ffff888097b95000 R15: ffff888097b95228 >> io_sqe_files_unregister+0x7d/0x2f0 fs/io_uring.c:4623 >> io_ring_ctx_free fs/io_uring.c:5575 [inline] >> io_ring_ctx_wait_and_kill+0x430/0x9a0 fs/io_uring.c:5644 >> io_uring_release+0x42/0x50 fs/io_uring.c:5652 >> __fput+0x2ff/0x890 fs/file_table.c:280 >> ____fput+0x16/0x20 fs/file_table.c:313 >> task_work_run+0x145/0x1c0 kernel/task_work.c:113 >> exit_task_work include/linux/task_work.h:22 [inline] >> do_exit+0x909/0x2f20 kernel/exit.c:797 >> do_group_exit+0x135/0x360 kernel/exit.c:895 >> get_signal+0x47c/0x24f0 kernel/signal.c:2734 >> do_signal+0x87/0x1700 arch/x86/kernel/signal.c:815 >> exit_to_usermode_loop+0x286/0x380 arch/x86/entry/common.c:160 >> prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline] >> syscall_return_slowpath arch/x86/entry/common.c:278 [inline] >> do_syscall_64+0x676/0x790 arch/x86/entry/common.c:304 >> entry_SYSCALL_64_after_hwframe+0x49/0xbe > > Flush work before killing. > > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -4618,10 +4618,10 @@ static int io_sqe_files_unregister(struc > if (!data) > return -ENXIO; > > + flush_work(&data->ref_work); > percpu_ref_kill_and_confirm(&data->refs, io_file_ref_kill); > wait_for_completion(&data->done); > percpu_ref_exit(&data->refs); > - flush_work(&data->ref_work); > > __io_sqe_files_unregister(ctx); > nr_tables = DIV_ROUND_UP(ctx->nr_user_files, IORING_MAX_FILES_TABLE); Oh indeed, good catch! Thanks, I'll fold this in. -- Jens Axboe
