Re: [syzbot] WARNING in nested_vmx_vmexit

syzbot
2021-12-07T11:20:25Z

syzbot has found a reproducer for the following issue on:

HEAD commit: f80ef9e49fdf Merge tag 'docs-5.16-3' of git://git.lwn.net/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15b11d89b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=7d5e878e3399b6cc
dashboard link: https://syzkaller.appspot.com/bug?extid=f1d2136db9c80d4733e8
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1603533ab00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=175b5f3db00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f1d2136db9c80d4733e8@syzkaller.appspotmail.com

L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for details.
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WARNING: CPU: 0 PID: 6503 at arch/x86/kvm/vmx/nested.c:4550 nested_vmx_vmexit+0x16bd/0x17e0 arch/x86/kvm/vmx/nested.c:4549
Modules linked in:
CPU: 0 PID: 6503 Comm: syz-executor767 Not tainted 5.16.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:nested_vmx_vmexit+0x16bd/0x17e0 arch/x86/kvm/vmx/nested.c:4549
Code: df e8 07 8e a9 00 e9 b1 f7 ff ff 89 d9 80 e1 07 38 c1 0f 8c 51 eb ff ff 48 89 df e8 3d 8d a9 00 e9 44 eb ff ff e8 53 b9 5d 00 <0f> 0b e9 2e f8 ff ff e8 47 b9 5d 00 0f 0b e9 00 f1 ff ff 89 e9 80
RSP: 0018:ffffc90001a5fa50 EFLAGS: 00010293
RAX: ffffffff8126de2d RBX: 0000000000000000 RCX: ffff88807482d700
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000007
RBP: 0000000000000001 R08: ffffffff8126d650 R09: ffffed10041fb808
R10: ffffed10041fb808 R11: 0000000000000000 R12: ffff888020fdc000
R13: ffff8880797e8000 R14: dffffc0000000000 R15: 1ffff1100f2fd05d
FS: 0000000000000000(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020002000 CR3: 000000000c88e000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
vmx_leave_nested arch/x86/kvm/vmx/nested.c:6222 [inline]
nested_vmx_free_vcpu+0x83/0xc0 arch/x86/kvm/vmx/nested.c:330
vmx_free_vcpu+0x11f/0x2a0 arch/x86/kvm/vmx/vmx.c:6799
kvm_arch_vcpu_destroy+0x6b/0x240 arch/x86/kvm/x86.c:10990
kvm_vcpu_destroy+0x29/0x90 arch/x86/kvm/../../../virt/kvm/kvm_main.c:441
kvm_free_vcpus arch/x86/kvm/x86.c:11427 [inline]
kvm_arch_destroy_vm+0x3ef/0x6b0 arch/x86/kvm/x86.c:11546
kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:1189 [inline]
kvm_put_kvm+0x751/0xe40 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1220
kvm_vm_release+0x42/0x50 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1243
__fput+0x3fc/0x870 fs/file_table.c:280
task_work_run+0x146/0x1c0 kernel/task_work.c:164
exit_task_work include/linux/task_work.h:32 [inline]
do_exit+0x705/0x24f0 kernel/exit.c:832
do_group_exit+0x168/0x2d0 kernel/exit.c:929
__do_sys_exit_group+0x13/0x20 kernel/exit.c:940
__se_sys_exit_group+0x10/0x10 kernel/exit.c:938
__x64_sys_exit_group+0x37/0x40 kernel/exit.c:938
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7fe968c95c09
Code: Unable to access opcode bytes at RIP 0x7fe968c95bdf.
RSP: 002b:00007ffc762ba918 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007fe968d09270 RCX: 00007fe968c95c09
RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffffffffffc0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fe968d09270
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001