general protection fault in finish_task_switch (2)

general protection fault in finish_task_switch (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    8c8399e0a3fb Add linux-next specific files for 20180806
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=16c6b8e2400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1b6bc1781e49e93e
dashboard link: https://syzkaller.appspot.com/bug?extid=1f56df64bfb3c29dde6f
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+1f56df64bfb3c29dde6f@syzkaller.appspotmail.com

kasan: CONFIG_KASAN_INLINE enabled
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
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
  vmwrite_error+0x4c/0x60 arch/x86/kvm/vmx.c:2201
CPU: 0 PID: 9256 Comm: syz-executor2 Not tainted 4.18.0-rc8-next-20180806+  
#32
  __vmcs_writel arch/x86/kvm/vmx.c:2211 [inline]
  vmcs_writel arch/x86/kvm/vmx.c:2251 [inline]
  vmx_vcpu_load+0xcdb/0xfe0 arch/x86/kvm/vmx.c:2917
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__fire_sched_in_preempt_notifiers kernel/sched/core.c:2481  
[inline]
RIP: 0010:fire_sched_in_preempt_notifiers kernel/sched/core.c:2487 [inline]
RIP: 0010:finish_task_switch+0x538/0x870 kernel/sched/core.c:2679
Code: 89 e1 48 c1 e9 03 42 80 3c 39 00 0f 85 ab 01 00 00 4d 8b 24 24 4d 85  
e4 0f 84 e3 fc ff ff 49 8d 7c 24 10 48 89 f9 48 c1 e9 03 <42> 80 3c 39 00  
74 a5 e8 1c e8 67 00 eb 9e 80 3d 80 e4 31 07 00 0f
RSP: 0018:ffff8801977a7980 EFLAGS: 00010a06
RAX: 0000000000000000 RBX: ffff8801db02ca40 RCX: 1bd5a00000000022
RDX: 0000000000040000 RSI: ffffffff810edd32 RDI: dead000000000110
RBP: ffff8801977a7a68 R08: ffff88019386a080 R09: fffffbfff1107d28
R10: fffffbfff1107d28 R11: 0000000000000003 R12: dead000000000100
  kvm_arch_vcpu_load+0x22b/0x940 arch/x86/kvm/x86.c:3081
R13: ffff88019549c240 R14: 0000000000000000 R15: dffffc0000000000
FS:  00007fd2dc8cf700(0000) GS:ffff8801db000000(0000) knlGS:0000000000000000
  kvm_sched_in+0x82/0xa0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3975
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  __fire_sched_in_preempt_notifiers kernel/sched/core.c:2481 [inline]
  fire_sched_in_preempt_notifiers kernel/sched/core.c:2487 [inline]
  finish_task_switch+0x50d/0x870 kernel/sched/core.c:2679
CR2: 0000001b2fb21000 CR3: 0000000190863000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  context_switch kernel/sched/core.c:2826 [inline]
  __schedule+0x884/0x1ec0 kernel/sched/core.c:3471
  context_switch kernel/sched/core.c:2826 [inline]
  __schedule+0x884/0x1ec0 kernel/sched/core.c:3471
  preempt_schedule_common+0x22/0x60 kernel/sched/core.c:3595
  schedule+0xfb/0x450 kernel/sched/core.c:3515
  _cond_resched+0x1d/0x30 kernel/sched/core.c:4961
  __mutex_lock_common kernel/locking/mutex.c:908 [inline]
  __mutex_lock+0x13d/0x1700 kernel/locking/mutex.c:1073
  exit_to_usermode_loop+0x22f/0x380 arch/x86/entry/common.c:152
  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: 0033:0x456cb9
Code: fd b4 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 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fd2dc8cecf8 EFLAGS: 00000246
  ORIG_RAX: 00000000000000ca
RAX: 0000000000000001 RBX: 0000000000930148 RCX: 0000000000456cb9
RDX: 0000000000000016 RSI: 0000000000000001 RDI: 000000000093014c
RBP: 0000000000930140 R08: 0000000000000000 R09: 0000000000000000
  mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1088
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000093014c
R13: 00007ffd09c12e5f R14: 00007fd2dc8cf9c0 R15: 0000000000000001
  arch_jump_label_transform+0x1b/0x40 arch/x86/kernel/jump_label.c:112
Modules linked in:
  __jump_label_update+0x16e/0x1a0 kernel/jump_label.c:375
  jump_label_update+0x151/0x2e0 kernel/jump_label.c:760
Dumping ftrace buffer:
  static_key_slow_inc_cpuslocked+0x341/0x430 kernel/jump_label.c:110
    (ftrace buffer empty)
---[ end trace de1ac742ecfe90a2 ]---
RIP: 0010:__fire_sched_in_preempt_notifiers kernel/sched/core.c:2481  
[inline]
RIP: 0010:fire_sched_in_preempt_notifiers kernel/sched/core.c:2487 [inline]
RIP: 0010:finish_task_switch+0x538/0x870 kernel/sched/core.c:2679
Code: 89 e1 48 c1 e9 03 42 80 3c 39 00 0f 85 ab 01 00 00 4d 8b 24 24 4d 85  
e4 0f 84 e3 fc ff ff 49 8d 7c 24 10 48 89 f9 48 c1 e9 03 <42> 80 3c 39 00  
74 a5 e8 1c e8 67 00 eb 9e 80 3d 80 e4 31 07 00 0f
RSP: 0018:ffff8801977a7980 EFLAGS: 00010a06
  static_key_slow_inc+0x1a/0x30 kernel/jump_label.c:125
  kvm_arch_vcpu_init+0x300/0x830 arch/x86/kvm/x86.c:8710
  kvm_vcpu_init+0x2fb/0x420 arch/x86/kvm/../../../virt/kvm/kvm_main.c:317
RAX: 0000000000000000 RBX: ffff8801db02ca40 RCX: 1bd5a00000000022
  vmx_create_vcpu+0x14c/0x2980 arch/x86/kvm/vmx.c:10665
RDX: 0000000000040000 RSI: ffffffff810edd32 RDI: dead000000000110
RBP: ffff8801977a7a68 R08: ffff88019386a080 R09: fffffbfff1107d28
R10: fffffbfff1107d28 R11: 0000000000000003 R12: dead000000000100
R13: ffff88019549c240 R14: 0000000000000000 R15: dffffc0000000000
FS:  00007fd2dc8cf700(0000) GS:ffff8801db000000(0000) knlGS:0000000000000000
  kvm_arch_vcpu_create+0xe5/0x220 arch/x86/kvm/x86.c:8398
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  kvm_vm_ioctl_create_vcpu arch/x86/kvm/../../../virt/kvm/kvm_main.c:2476  
[inline]
  kvm_vm_ioctl+0x488/0x1d80 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2977
CR2: 0000001b2fb21000 CR3: 0000000190863000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
This bug is generated by a bot. It may contain errors.
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https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with  
syzbot.

Re: general protection fault in finish_task_switch (2)

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    778a33959a8a Merge tag 'please-pull-noboot' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14a5385a400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=214e4990bd49329f
dashboard link: https://syzkaller.appspot.com/bug?extid=1f56df64bfb3c29dde6f
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
userspace arch: i386
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=13ffa561400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10023961400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+1f56df64bfb3c29dde6f@syzkaller.appspotmail.com

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
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.
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
CPU: 0 PID: 4489 Comm: syz-executor233 Not tainted 4.18.0+ #103
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__fire_sched_in_preempt_notifiers kernel/sched/core.c:2481  
[inline]
RIP: 0010:fire_sched_in_preempt_notifiers kernel/sched/core.c:2487 [inline]
RIP: 0010:finish_task_switch+0x538/0x870 kernel/sched/core.c:2679
Code: 89 e1 48 c1 e9 03 42 80 3c 39 00 0f 85 ab 01 00 00 4d 8b 24 24 4d 85  
e4 0f 84 e3 fc ff ff 49 8d 7c 24 10 48 89 f9 48 c1 e9 03 <42> 80 3c 39 00  
74 a5 e8 8c a5 67 00 eb 9e 80 3d 8b c3 32 07 00 0f
RSP: 0018:ffff8801ac0ff058 EFLAGS: 00010a06
RAX: 0000000000000000 RBX: ffff8801db02cc40 RCX: 1bd5a00000000022
RDX: 0000000000000000 RSI: ffffffff810ed162 RDI: dead000000000110
RBP: ffff8801ac0ff140 R08: ffff8801acb8c300 R09: ffffed003b221b6c
R10: ffffed003b221b6c R11: ffff8801d910db67 R12: dead000000000100
R13: ffff8801ca5e0040 R14: 0000000000000000 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8801db000000(0063) knlGS:00000000f7f07b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00007f1304e0b000 CR3: 00000001acab3000 CR4: 00000000001426f0
Call Trace:
  context_switch kernel/sched/core.c:2826 [inline]
  __schedule+0x884/0x1df0 kernel/sched/core.c:3471
  schedule+0xfb/0x450 kernel/sched/core.c:3515
  freezable_schedule include/linux/freezer.h:172 [inline]
  futex_wait_queue_me+0x3f9/0x840 kernel/futex.c:2530
  futex_wait+0x45b/0xa20 kernel/futex.c:2645
  do_futex+0x336/0x27d0 kernel/futex.c:3527
  __do_compat_sys_futex kernel/futex_compat.c:201 [inline]
  __se_compat_sys_futex kernel/futex_compat.c:175 [inline]
  __ia32_compat_sys_futex+0x3d9/0x5f0 kernel/futex_compat.c:175
  do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline]
  do_fast_syscall_32+0x34d/0xfb2 arch/x86/entry/common.c:397
  entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7f0bca9
Code: 55 08 8b 88 64 cd ff ff 8b 98 68 cd ff ff 89 c8 85 d2 74 02 89 0a 5b  
5d c3 8b 04 24 c3 8b 1c 24 c3 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90  
90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000f7f071ec EFLAGS: 00000296 ORIG_RAX: 00000000000000f0
RAX: ffffffffffffffda RBX: 00000000080fb008 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00000000c080aebe R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
Dumping ftrace buffer:
    (ftrace buffer empty)
---[ end trace a4bb2f1beb6735f0 ]---
RIP: 0010:__fire_sched_in_preempt_notifiers kernel/sched/core.c:2481  
[inline]
RIP: 0010:fire_sched_in_preempt_notifiers kernel/sched/core.c:2487 [inline]
RIP: 0010:finish_task_switch+0x538/0x870 kernel/sched/core.c:2679
Code: 89 e1 48 c1 e9 03 42 80 3c 39 00 0f 85 ab 01 00 00 4d 8b 24 24 4d 85  
e4 0f 84 e3 fc ff ff 49 8d 7c 24 10 48 89 f9 48 c1 e9 03 <42> 80 3c 39 00  
74 a5 e8 8c a5 67 00 eb 9e 80 3d 8b c3 32 07 00 0f
RSP: 0018:ffff8801ac0ff058 EFLAGS: 00010a06
RAX: 0000000000000000 RBX: ffff8801db02cc40 RCX: 1bd5a00000000022
RDX: 0000000000000000 RSI: ffffffff810ed162 RDI: dead000000000110
RBP: ffff8801ac0ff140 R08: ffff8801acb8c300 R09: ffffed003b221b6c
R10: ffffed003b221b6c R11: ffff8801d910db67 R12: dead000000000100
R13: ffff8801ca5e0040 R14: 0000000000000000 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8801db000000(0063) knlGS:00000000f7f07b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00007f1304e0b000 CR3: 00000001acab3000 CR4: 00000000001426f0

Re: general protection fault in finish_task_switch (2)

[Peter Zijlstra]

On Tue, Aug 21, 2018 at 02:28:02PM -0700, syzbot wrote:
> syzbot has found a reproducer for the following crash on:
> 
> HEAD commit:    778a33959a8a Merge tag 'please-pull-noboot' of git://git.k..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14a5385a400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=214e4990bd49329f
> dashboard link: https://syzkaller.appspot.com/bug?extid=1f56df64bfb3c29dde6f
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> userspace arch: i386
> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=13ffa561400000

FWIW the lack of whitespace between "repro:" and the URL makes it hard
to copy paste.

> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10023961400000


> RIP: 0010:__fire_sched_in_preempt_notifiers kernel/sched/core.c:2481

That repro thing does something dodgy with KVM, which then corrupts the
premption notifier thing. I'm sufficiently KVM clueless to not really
know where to start looking though..

Re: general protection fault in finish_task_switch (2)

[Paolo Bonzini]

On 22/08/2018 11:08, Peter Zijlstra wrote:
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10023961400000
> 
>> RIP: 0010:__fire_sched_in_preempt_notifiers kernel/sched/core.c:2481
> That repro thing does something dodgy with KVM, which then corrupts the
> premption notifier thing. I'm sufficiently KVM clueless to not really
> know where to start looking though..

It seems to be a reference counting issue, or something like that.  I'm
looking at it...

Paolo

Re: general protection fault in finish_task_switch (2)

[Dmitry Vyukov]

On Wed, Aug 22, 2018 at 2:08 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Tue, Aug 21, 2018 at 02:28:02PM -0700, syzbot wrote:
>> syzbot has found a reproducer for the following crash on:
>>
>> HEAD commit:    778a33959a8a Merge tag 'please-pull-noboot' of git://git.k..
>> git tree:       upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=14a5385a400000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=214e4990bd49329f
>> dashboard link: https://syzkaller.appspot.com/bug?extid=1f56df64bfb3c29dde6f
>> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
>> userspace arch: i386
>> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=13ffa561400000
>
> FWIW the lack of whitespace between "repro:" and the URL makes it hard
> to copy paste.

Fixed by:
https://github.com/google/syzkaller/commit/307deaee5e23e4585d4b408ebcf329b9dc8ebdb4
Thanks

>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10023961400000
>
>
>> RIP: 0010:__fire_sched_in_preempt_notifiers kernel/sched/core.c:2481
>
> That repro thing does something dodgy with KVM, which then corrupts the
> premption notifier thing. I'm sufficiently KVM clueless to not really
> know where to start looking though..