Re: WARNING: ODEBUG bug in del_timer

[Dmitry Vyukov]

On Wed, Oct 16, 2019 at 11:59 AM zzoru <zzoru007@xxxxxxxxx> wrote:
>
> We found the following crash on Linux 5.4-rc1 (Not patched in currnet
> HEAD commit 3b1f00aceb7a67bf079a5a64aa5c6baf78a8f442)
> with our customized syzkaller.

Hi zzoru,

Do you mind sharing what customizations you did to syzkaller? Are
these related to USB? I've noticed several reports were related to USB
subsystem.

> ODEBUG: assert_init not available (active state 0) object type:
> timer_list hint: 0x0
> WARNING: CPU: 0 PID: 141 at linux/lib/debugobjects.c:484
> debug_print_object+0x15e/0x220 linux/lib/debugobjects.c:481
> Kernel panic - not syncing: panic_on_warn set ...
> CPU: 0 PID: 141 Comm: kworker/0:3 Not tainted 5.4.0-rc1 #5
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
> Workqueue: usb_hub_wq hub_event
> Call Trace:
>  __dump_stack linux/lib/dump_stack.c:77 [inline]
>  dump_stack+0x7c/0xbb linux/lib/dump_stack.c:113
>  panic+0x205/0x48e linux/kernel/panic.c:220
>  __warn+0x19c/0x1c0 linux/kernel/panic.c:581
>  report_bug+0x1a9/0x2b0 linux/lib/bug.c:195
>  fixup_bug.part.11+0x32/0x80 linux/arch/x86/kernel/traps.c:179
>  fixup_bug linux/arch/x86/include/asm/irqflags.h:54 [inline]
>  do_error_trap+0xf5/0x160 linux/arch/x86/kernel/traps.c:272
>  do_invalid_op+0x31/0x40 linux/arch/x86/kernel/traps.c:291
>  invalid_op+0x23/0x30 linux/arch/x86/entry/entry_64.S:1028
> RIP: 0010:debug_print_object+0x15e/0x220 linux/lib/debugobjects.c:481
> Code: 3c dd 80 05 9a 85 48 89 fa 48 c1 ea 03 80 3c 02 00 75 7f 48 8b
> 14 dd 80 05 9a 85 4c 89 ee 48 c7 c7 00 fb 99 85 e8 d2 a7 43 ff <0f> 0b
> 83 05 cd bd 70 05 01 48 83 c4 18 5b 5d 41 5c 41 5d 41 5e c3
> RSP: 0018:ffff888017017668 EFLAGS: 00010282
> RAX: 0000000000000000 RBX: 0000000000000005 RCX: ffffffff814153b0
> RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff88801a41f730
> RBP: 0000000000000001 R08: ffffed1003483ee7 R09: ffffed1003483ee7
> R10: 0000000000000001 R11: ffffed1003483ee6 R12: ffffffff86908460
> R13: ffffffff859a01a0 R14: ffffffff812b6bc0 R15: ffff888017fb0420
>  debug_object_assert_init+0x290/0x430 linux/lib/debugobjects.c:866
>  debug_timer_assert_init linux/kernel/time/timer.c:729 [inline]
>  debug_assert_init linux/kernel/time/timer.c:774 [inline]
>  del_timer+0x67/0xf0 linux/kernel/time/timer.c:1196
>  realtek_cr_destructor+0x5a/0x90 linux/drivers/usb/storage/realtek_cr.c:937
>  usb_stor_release_resources linux/drivers/usb/storage/usb.c:817 [inline]
>  release_everything+0xc0/0x2c0 linux/drivers/usb/storage/usb.c:879
>  usb_unbind_interface+0x19f/0x810 linux/drivers/usb/core/driver.c:423
>  __device_release_driver linux/drivers/base/dd.c:1134 [inline]
>  device_release_driver_internal+0x429/0x4f0 linux/drivers/base/dd.c:1165
>  bus_remove_device+0x2d1/0x490 linux/drivers/base/bus.c:532
>  device_del+0x403/0xaa0 linux/drivers/base/core.c:2375
>  usb_disable_device+0x1d7/0x5f0 linux/drivers/usb/core/message.c:1237
>  usb_disconnect+0x25a/0x840 linux/drivers/usb/core/hub.c:2199
>  hub_port_connect linux/drivers/usb/core/hub.c:4949 [inline]
>  hub_port_connect_change linux/drivers/usb/core/hub.c:5213 [inline]
>  port_event linux/drivers/usb/core/hub.c:5359 [inline]
>  hub_event+0x11f5/0x3610 linux/drivers/usb/core/hub.c:5441
>  process_one_work+0x8b5/0x17c0 linux/kernel/workqueue.c:2269
>  worker_thread+0x82/0xb80 linux/kernel/workqueue.c:2415
>  kthread+0x325/0x3e0 linux/kernel/kthread.c:255
>  ret_from_fork+0x24/0x30 linux/arch/x86/entry/entry_64.S:352
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Kernel Offset: disabled
>
> Following is my analysis of this bug (Just add some comments in source code):
> https://github.com/torvalds/linux/blob/e0703556644a531e50b5dc61b9f6ea83af5f6604/drivers/usb/storage/realtek_cr.c#L887-L891
> static int realtek_cr_autosuspend_setup(struct us_data *us)
> {
>     ...
>     if (retval != STATUS_SUCCESS) {
>         usb_stor_dbg(us, "Read status fail\n");
>         return -EIO; // Error!
>     }
>     ...
>     timer_setup(&chip->rts51x_suspend_timer, rts51x_suspend_timer_fn,
> 0); // rts51x_suspend_timer wasn't be initialized. When
> realtek_cr_autosuspend_setup just returns an error.
> }
>
>
> https://github.com/torvalds/linux/blob/e0703556644a531e50b5dc61b9f6ea83af5f6604/drivers/usb/storage/realtek_cr.c#L1010-L1012
>
> #ifdef CONFIG_REALTEK_AUTOPM
> if (ss_en)
>     realtek_cr_autosuspend_setup(us); // There isn't any check about
> return code.
> #endif
>
> https://github.com/torvalds/linux/blob/e0703556644a531e50b5dc61b9f6ea83af5f6604/drivers/usb/storage/realtek_cr.c#L936-L939
> static void realtek_cr_destructor(void *extra)
> {
>     ...
>     if (ss_en) {
>         del_timer(&chip->rts51x_suspend_timer); // Ouch! :(
>         chip->timer_expires = 0;
>     }
>     ...
> }