Re: WARNING in ep_poll_callback

[Dmitry Vyukov]

On Tue, Jan 8, 2019 at 6:59 AM syzbot
<syzbot+aea82bf9ee6ffd9a79d9@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    139287cc2cc0 Add linux-next specific files for 20190108
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=16f563d7400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=1521b074ff5a5bdf
> dashboard link: https://syzkaller.appspot.com/bug?extid=aea82bf9ee6ffd9a79d9
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.

Looks like caused by:

commit f92cacf118171208f62519d92502a8dd0341286d
Author: Roman Penyaev
Date:   Tue Jan 8 12:15:44 2019 +1100

    epoll: loosen irq safety in ep_poll_callback()


> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+aea82bf9ee6ffd9a79d9@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> ------------[ cut here ]------------
> IRQs not disabled as expected
> WARNING: CPU: 1 PID: 27199 at fs/eventpoll.c:1224
> ep_poll_callback+0x77e/0x1450 fs/eventpoll.c:1224
> Kernel panic - not syncing: panic_on_warn set ...
> CPU: 1 PID: 27199 Comm: syz-executor4 Not tainted 5.0.0-rc1-next-20190108 #7
> 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+0x1db/0x2d0 lib/dump_stack.c:113
>   panic+0x2cb/0x65c kernel/panic.c:214
>   __warn.cold+0x20/0x48 kernel/panic.c:571
>   report_bug+0x263/0x2b0 lib/bug.c:186
>   fixup_bug arch/x86/kernel/traps.c:178 [inline]
>   fixup_bug arch/x86/kernel/traps.c:173 [inline]
>   do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
>   do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:290
>   invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
> RIP: 0010:ep_poll_callback+0x77e/0x1450 fs/eventpoll.c:1224
> Code: ff 44 89 ee e8 63 84 98 ff 45 84 ed 0f 85 4a fa ff ff e8 15 83 98 ff
> 48 c7 c7 00 69 56 88 c6 05 a1 b2 6e 08 01 e8 52 c8 61 ff <0f> 0b e9 2b fa
> ff ff e8 f6 82 98 ff 48 8d 7b 30 48 b8 00 00 00 00
> RSP: 0018:ffff8880533776a0 EFLAGS: 00010282
> RAX: 0000000000000000 RBX: ffff88804df7ee40 RCX: ffffc9000de3b000
> RDX: 0000000000012c8d RSI: ffffffff816869f6 RDI: 0000000000000005
> RBP: ffff888053377880 R08: ffff8880a078a700 R09: ffff8880a078aff0
> R10: ffff8880a078a700 R11: 0000000000000000 R12: ffff888053377858
> R13: 0000000000000000 R14: ffff88804df7ee90 R15: 0000000000000000
>   __wake_up_common+0x1d3/0x7d0 kernel/sched/wait.c:92
>   __wake_up_locked+0x11/0x20 kernel/sched/wait.c:154
>   fuse_abort_conn+0xd01/0x1200 fs/fuse/dev.c:2212
>   fuse_sb_destroy+0xd3/0x1d0 fs/fuse/inode.c:1245
>   fuse_kill_sb_anon+0x16/0x30 fs/fuse/inode.c:1256
>   deactivate_locked_super+0x9a/0x100 fs/super.c:331
>   deactivate_super fs/super.c:362 [inline]
>   deactivate_super+0x2ab/0x320 fs/super.c:358
>   cleanup_mnt+0xbf/0x160 fs/namespace.c:1140
>   __cleanup_mnt+0x16/0x20 fs/namespace.c:1147
>   task_work_run+0x1f4/0x2b0 kernel/task_work.c:113
>   tracehook_notify_resume include/linux/tracehook.h:188 [inline]
>   exit_to_usermode_loop+0x32a/0x3b0 arch/x86/entry/common.c:166
>   prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
>   syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
>   do_syscall_64+0x696/0x800 arch/x86/entry/common.c:293
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x457ec9
> Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
> 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
> ff 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f19fdcaec78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
> RAX: 0000000000000000 RBX: 0000000000000002 RCX: 0000000000457ec9
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000040
> RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f19fdcaf6d4
> R13: 00000000004c6ab2 R14: 00000000004dbdb8 R15: 00000000ffffffff
> Kernel Offset: disabled
> Rebooting in 86400 seconds..
>
>
> ---
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