Re: WARNING in vkms_gem_free_object

[Daniel Vetter]

On Sun, Oct 13, 2019 at 07:49:08PM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    8ada228a Add linux-next specific files for 20191011
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=14c30b1b600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=7cf4eed5fe42c31a
> dashboard link: https://syzkaller.appspot.com/bug?extid=e7ad70d406e74d8fc9d0
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1087d31b600000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15e27c53600000
> 
> The bug was bisected to:
> 
> commit 94e2ec3f7fef86506293a448273b2b4ee21e6195
> Author: Oleg Vasilev <omrigann@xxxxxxxxx>
> Date:   Mon Sep 30 15:59:24 2019 +0000
> 
>     drm/vkms: prime import support
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=15ef2d57600000
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=17ef2d57600000
> console output: https://syzkaller.appspot.com/x/log.txt?x=13ef2d57600000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+e7ad70d406e74d8fc9d0@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: 94e2ec3f7fef ("drm/vkms: prime import support")

Oleg, will you be looking at this? With the reproducer and full drm
debugging enabled it shouldn't be too hard to figure out what's going on
heere ...
-Daniel

> 
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 9040 at drivers/gpu/drm/vkms/vkms_gem.c:37
> vkms_gem_free_object+0x92/0xb0 drivers/gpu/drm/vkms/vkms_gem.c:37
> Kernel panic - not syncing: panic_on_warn set ...
> CPU: 1 PID: 9040 Comm: syz-executor028 Not tainted 5.4.0-rc2-next-20191011
> #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+0x172/0x1f0 lib/dump_stack.c:113
>  panic+0x2e3/0x75c kernel/panic.c:221
>  __warn.cold+0x2f/0x35 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:1028
> RIP: 0010:vkms_gem_free_object+0x92/0xb0 drivers/gpu/drm/vkms/vkms_gem.c:37
> Code: 44 68 7f fd 49 8d bc 24 f8 01 00 00 e8 c7 8d 64 fd 4c 89 e7 e8 3f 39
> ae ff 4c 89 e7 e8 f7 9a ba fd 41 5c 5d c3 e8 1e 68 7f fd <0f> 0b eb a2 e8 15
> 68 7f fd 0f 0b eb c8 e8 2c e7 ba fd eb b6 e8 25
> RSP: 0018:ffff8880971df9e8 EFLAGS: 00010293
> RAX: ffff8880989c2200 RBX: ffffffff894e5000 RCX: ffffffff83a1eda6
> RDX: 0000000000000000 RSI: ffffffff83f3ab02 RDI: ffff8880a8c4fa78
> RBP: ffff8880971df9f0 R08: ffff8880989c2200 R09: ffffed1012e3bf36
> R10: ffffed1012e3bf35 R11: 0000000000000003 R12: ffff8880a8c4f800
> R13: ffff8880a3ab8000 R14: ffffffff83f3aa70 R15: ffff8880a3ab8020
>  drm_gem_object_free+0x100/0x220 drivers/gpu/drm/drm_gem.c:983
>  kref_put include/linux/kref.h:65 [inline]
>  drm_gem_object_put_unlocked drivers/gpu/drm/drm_gem.c:1017 [inline]
>  drm_gem_object_put_unlocked+0x127/0x170 drivers/gpu/drm/drm_gem.c:1002
>  drm_gem_object_handle_put_unlocked+0x1ad/0x2d0
> drivers/gpu/drm/drm_gem.c:239
>  drm_gem_object_release_handle+0x102/0x1c0 drivers/gpu/drm/drm_gem.c:261
>  idr_for_each+0x138/0x250 lib/idr.c:208
>  drm_gem_release+0x27/0x40 drivers/gpu/drm/drm_gem.c:939
>  drm_file_free.part.0+0x7f4/0xc00 drivers/gpu/drm/drm_file.c:244
>  drm_file_free drivers/gpu/drm/drm_file.c:213 [inline]
>  drm_close_helper drivers/gpu/drm/drm_file.c:271 [inline]
>  drm_release+0x286/0x3f0 drivers/gpu/drm/drm_file.c:443
>  __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+0x904/0x2e60 kernel/exit.c:817
>  do_group_exit+0x135/0x360 kernel/exit.c:921
>  __do_sys_exit_group kernel/exit.c:932 [inline]
>  __se_sys_exit_group kernel/exit.c:930 [inline]
>  __x64_sys_exit_group+0x44/0x50 kernel/exit.c:930
>  do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x442bb8
> Code: Bad RIP value.
> RSP: 002b:00007ffd8fdc0b98 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000442bb8
> RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
> RBP: 00000000004c24c8 R08: 00000000000000e7 R09: ffffffffffffffd0
> R10: 00000000004002e0 R11: 0000000000000246 R12: 0000000000000001
> R13: 00000000006d41a0 R14: 0000000000000000 R15: 0000000000000000
> Kernel Offset: disabled
> Rebooting in 86400 seconds..
> 
> 
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx
> 
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch