Re: WARNING in free_loaded_vmcs (2)

[Paolo Bonzini]

Is there anything that was changed in syzkaller and is causing it to
find all these bugs?

Thanks,

Paolo

On 14/08/2018 14:46, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:ÂÂÂ 112cbae26d18 Merge branch 'linus' of
> git://git.kernel.org/..
> git tree:ÂÂÂÂÂÂ upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=161d8a3c400000
> kernel config:Â https://syzkaller.appspot.com/x/.config?x=152cb8ccd35b1f70
> dashboard link:
> https://syzkaller.appspot.com/bug?extid=01bc9e7a8a3f138b71cf
> compiler:ÂÂÂÂÂÂ gcc (GCC) 8.0.1 20180413 (experimental)
> 
> Unfortunately, I don't have any reproducer for this crash yet.
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+01bc9e7a8a3f138b71cf@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> WARNING: CPU: 1 PID: 5195 at arch/x86/kvm/vmx.c:4431
> free_loaded_vmcs+0x160/0x1b0 arch/x86/kvm/vmx.c:4431
> Kernel panic - not syncing: panic_on_warn set ...
> 
> CPU: 1 PID: 5195 Comm: syz-executor3 Not tainted 4.18.0-rc8+ #182
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
> Â__dump_stack lib/dump_stack.c:77 [inline]
> Âdump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
> Âpanic+0x238/0x4e7 kernel/panic.c:184
> Â__warn.cold.8+0x163/0x1ba kernel/panic.c:536
> Âreport_bug+0x252/0x2d0 lib/bug.c:186
> Âfixup_bug arch/x86/kernel/traps.c:178 [inline]
> Âdo_error_trap+0x1fc/0x4d0 arch/x86/kernel/traps.c:296
> Âdo_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
> Âinvalid_op+0x14/0x20 arch/x86/entry/entry_64.S:992
> RIP: 0010:free_loaded_vmcs+0x160/0x1b0 arch/x86/kvm/vmx.c:4431
> Code: 81 e8 64 25 53 00 48 89 da 48 b8 00 00 00 00 00 fc ff df 48 c1 ea
> 03 80 3c 02 00 75 49 4c 8b 23 e9 22 ff ff ff e8 50 5f 5f 00 <0f> 0b eb
> b0 e8 77 3b 9d 00 e9 f4 fe ff ff 48 89 df e8 8a 3b 9d 00
> RSP: 0018:ffff8801947bf780 EFLAGS: 00010293
> RAX: ffff88018fe4a680 RBX: ffff88018f95e3e8 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffffffff811cb900 RDI: ffff88018f95e3f0
> RBP: ffff8801947bf798 R08: ffffea0007544608 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801d5118000
> R13: 0000000000000001 R14: dffffc0000000000 R15: 0000000000000001
> Âvmx_free_vcpu+0x204/0x300 arch/x86/kvm/vmx.c:10299
> Âkvm_arch_vcpu_free arch/x86/kvm/x86.c:8314 [inline]
> Âkvm_free_vcpus arch/x86/kvm/x86.c:8763 [inline]
> Âkvm_arch_destroy_vm+0x365/0x7c0 arch/x86/kvm/x86.c:8860
> Âkvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:746 [inline]
> Âkvm_put_kvm+0x73f/0x1060 arch/x86/kvm/../../../virt/kvm/kvm_main.c:767
> Âkvm_vcpu_release+0x7b/0xa0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2397
> Â__fput+0x355/0x8b0 fs/file_table.c:209
> Â____fput+0x15/0x20 fs/file_table.c:243
> Âtask_work_run+0x1ec/0x2a0 kernel/task_work.c:113
> Âtracehook_notify_resume include/linux/tracehook.h:192 [inline]
> Âexit_to_usermode_loop+0x313/0x370 arch/x86/entry/common.c:166
> Âprepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
> Âsyscall_return_slowpath arch/x86/entry/common.c:268 [inline]
> Âdo_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
> Âentry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x410c41
> Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 34 19 00 00 c3
> 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c
> 24 48 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
> RSP: 002b:0000000000a3fdc0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
> RAX: 0000000000000000 RBX: 0000000000000007 RCX: 0000000000410c41
> RDX: 0000000000000000 RSI: 0000000000731000 RDI: 0000000000000006
> RBP: 0000000000000000 R08: ffffffffffffffff R09: ffffffffffffffff
> R10: 0000000000a3fcf0 R11: 0000000000000293 R12: 0000000000000007
> R13: 000000000008c6e7 R14: 0000000000000398 R15: badc0ffeebadface
> Dumping ftrace buffer:
> ÂÂ (ftrace buffer empty)
> 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#bug-status-tracking for how to communicate with
> syzbot.