WARNING in free_loaded_vmcs (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 112cbae26d18 Merge branch 'linus' of git://git.kernel.org/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=161d8a3c400000
kernel config: https://syzkaller.appspot.com/x/.config?x=152cb8ccd35b1f70
dashboard link: https://syzkaller.appspot.com/bug?extid=01bc9e7a8a3f138b71cf
compiler: 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+01bc9e...@syzkaller.appspotmail.com

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:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
panic+0x238/0x4e7 kernel/panic.c:184
__warn.cold.8+0x163/0x1ba kernel/panic.c:536
report_bug+0x252/0x2d0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
do_error_trap+0x1fc/0x4d0 arch/x86/kernel/traps.c:296
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
invalid_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
vmx_free_vcpu+0x204/0x300 arch/x86/kvm/vmx.c:10299
kvm_arch_vcpu_free arch/x86/kvm/x86.c:8314 [inline]
kvm_free_vcpus arch/x86/kvm/x86.c:8763 [inline]
kvm_arch_destroy_vm+0x365/0x7c0 arch/x86/kvm/x86.c:8860
kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:746 [inline]
kvm_put_kvm+0x73f/0x1060 arch/x86/kvm/../../../virt/kvm/kvm_main.c:767
kvm_vcpu_release+0x7b/0xa0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2397
__fput+0x355/0x8b0 fs/file_table.c:209
____fput+0x15/0x20 fs/file_table.c:243
task_work_run+0x1ec/0x2a0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:192 [inline]
exit_to_usermode_loop+0x313/0x370 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+0x6be/0x820 arch/x86/entry/common.c:293
entry_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:
(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.
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https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
syzbot.

[Paolo Bonzini]

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

Thanks,

Paolo

[Dmitry Vyukov]

On Tue, Aug 14, 2018 at 10:16 AM, Paolo Bonzini <pbon...@redhat.com> wrote:
> Is there anything that was changed in syzkaller and is causing it to
> find all these bugs?

Nothing has changed on syzkaller side as far as I can tell.

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[Paolo Bonzini]

On 14/08/2018 22:41, Dmitry Vyukov wrote:
> On Tue, Aug 14, 2018 at 10:16 AM, Paolo Bonzini <pbon...@redhat.com> wrote:
>> Is there anything that was changed in syzkaller and is causing it to
>> find all these bugs?
> Nothing has changed on syzkaller side as far as I can tell.

And the failures started to appear on 20180806 when I did the big KVM
update from 85eae57bbb0612387201635659be543aaac2109e to
8c154ff6ee99d2d467c3c964ef6a478ca7614155.

They all seem related to some use-after-free on exit, and there is a
reproducer at https://syzkaller.appspot.com/x/repro.c?x=122d6672400000,
but it doesn't immediately cause the failure for me.

Paolo

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: 60c1f89241d4 Merge tag 'dma-mapping-4.19-2' of git://git.i..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15022d5a400000
kernel config: https://syzkaller.appspot.com/x/.config?x=4c7e83258d6e0156

dashboard link: https://syzkaller.appspot.com/bug?extid=01bc9e7a8a3f138b71cf
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12a6513e400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+01bc9e...@syzkaller.appspotmail.com

IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
8021q: adding VLAN 0 to HW filter on device team0
L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and
https://www.kernel.org/doc/html/latest/admin-guide/l1tf.html for details.
WARNING: CPU: 1 PID: 4980 at arch/x86/kvm/vmx.c:4754
free_loaded_vmcs+0x160/0x1b0 arch/x86/kvm/vmx.c:4754

Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 4980 Comm: syz-executor0 Not tainted 4.19.0-rc2+ #220

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+0x1c9/0x2b4 lib/dump_stack.c:113
panic+0x238/0x4e7 kernel/panic.c:184
__warn.cold.8+0x163/0x1ba kernel/panic.c:536
report_bug+0x252/0x2d0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
do_error_trap+0x1fc/0x4d0 arch/x86/kernel/traps.c:296
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316

invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:993
RIP: 0010:free_loaded_vmcs+0x160/0x1b0 arch/x86/kvm/vmx.c:4754
Code: 81 e8 44 be 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 80 fc 5f 00 <0f> 0b eb b0 e8
b7 f9 9e 00 e9 f4 fe ff ff 48 89 df e8 ca f9 9e 00
RSP: 0018:ffff8801d06af748 EFLAGS: 00010293
RAX: ffff8801d068a500 RBX: ffff8801d0ab57a8 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff811cd2a0 RDI: ffff8801d0ab57b0
RBP: ffff8801d06af760 R08: ffff8801d068a500 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801c7166000

R13: 0000000000000001 R14: dffffc0000000000 R15: 0000000000000001

vmx_free_vcpu+0x204/0x300 arch/x86/kvm/vmx.c:10945
kvm_arch_vcpu_free arch/x86/kvm/x86.c:8420 [inline]
kvm_free_vcpus arch/x86/kvm/x86.c:8870 [inline]
kvm_arch_destroy_vm+0x365/0x7c0 arch/x86/kvm/x86.c:8967
kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:752 [inline]
kvm_put_kvm+0x73f/0x1060 arch/x86/kvm/../../../virt/kvm/kvm_main.c:773
kvm_vcpu_release+0x7b/0xa0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2407
__fput+0x38a/0xa40 fs/file_table.c:278
____fput+0x15/0x20 fs/file_table.c:309
task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:193 [inline]
exit_to_usermode_loop+0x318/0x380 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+0x6be/0x820 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

RIP: 0033:0x410c30
Code: 01 f0 ff ff 0f 83 60 19 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f
44 00 00 83 3d 5d 53 63 00 00 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

RSP: 002b:00007ffeb3e8ae98 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000006 RCX: 0000000000410c30
RDX: 0000001b32e20000 RSI: 00000000007334f0 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004129f0
R13: 0000000000412a80 R14: 0000000000000000 R15: badc0ffeebadface

[syzbot]

syzbot has bisected this bug to:

commit 8fcc4b5923af5de58b80b53a069453b135693304
Author: Jim Mattson <jmat...@google.com>
Date: Tue Jul 10 09:27:20 2018 +0000

kvm: nVMX: Introduce KVM_CAP_NESTED_STATE

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17fba63f200000
start commit: 60c1f892 Merge tag 'dma-mapping-4.19-2' of git://git.infra..
git tree: upstream
final crash: https://syzkaller.appspot.com/x/report.txt?x=1407a63f200000
console output: https://syzkaller.appspot.com/x/log.txt?x=1007a63f200000

kernel config: https://syzkaller.appspot.com/x/.config?x=4c7e83258d6e0156
dashboard link: https://syzkaller.appspot.com/bug?extid=01bc9e7a8a3f138b71cf

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12a6513e400000

Reported-by: syzbot+01bc9e...@syzkaller.appspotmail.com
Fixes: 8fcc4b5923af ("kvm: nVMX: Introduce KVM_CAP_NESTED_STATE")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[Sean Christopherson]

Blech, this is horribly stale. Fixed by commit 5bea5123cbf0 ("KVM: VMX:
check nested state and CR4.VMXE against SMM").

#syz fix: KVM: VMX: check nested state and CR4.VMXE against SMM