This report should be sent to KVM people. I guess that a lack of serialization between kvm_create_vm_debugfs() from kvm_dev_ioctl_create_vm() and kvm_destroy_vm_debugfs() from kvm_destroy_vm() is causing a race on kvm->debugfs_dentry when kvm_uevent_notify_change() called dentry_path_raw(kvm->debugfs_dentry). On 2019/01/30 20:32, syzbot wrote: > syzbot has found a reproducer for the following crash on: > > HEAD commit: 02495e76ded5 Add linux-next specific files for 20190130 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=106161ef400000 > kernel config: https://syzkaller.appspot.com/x/.config?x=a2b2e9c0bc43c14d > dashboard link: https://syzkaller.appspot.com/bug?extid=7857962b4d45e602b8ad > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1182e5b8c00000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+7857962b4d45e602b8ad@xxxxxxxxxxxxxxxxxxxxxxxxx > > kasan: CONFIG_KASAN_INLINE enabled > kasan: GPF could be caused by NULL-ptr deref or user memory access > general protection fault: 0000 [#1] PREEMPT SMP KASAN > CPU: 0 PID: 8239 Comm: syz-executor4 Not tainted 5.0.0-rc4-next-20190130 #22 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > RIP: 0010:__dentry_path+0x2a5/0xaa0 fs/d_path.c:344 > Code: 00 00 e8 1e 9d 9f ff 48 c7 c7 68 26 81 89 e8 72 c4 14 06 e8 0d 9d 9f ff 48 8b 85 00 ff ff ff 48 8d 78 40 48 89 f8 48 c1 e8 03 <42> 80 3c 38 00 0f 85 b0 07 00 00 48 8b 85 00 ff ff ff 4c 8b 68 40 > RSP: 0018:ffff88808ab5f8a8 EFLAGS: 00010207 > RAX: 0000000000000005 RBX: 0000000000000000 RCX: ffffffff81e27f21 > RDX: 0000000000000000 RSI: ffffffff81e27c43 RDI: 000000000000002f > RBP: ffff88808ab5f9d0 R08: ffff88809edd4280 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000000 R12: ffff88808ab5f9a8 > R13: 0000000000000000 R14: 0000000000000c78 R15: dffffc0000000000 > FS: 00007f69a6d18700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 000000000144a008 CR3: 00000000a1190000 CR4: 00000000001426f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > dentry_path_raw+0x26/0x30 fs/d_path.c:371 > kvm_uevent_notify_change.part.0+0x213/0x440 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4050 > kvm_uevent_notify_change arch/x86/kvm/../../../virt/kvm/kvm_main.c:4017 [inline] > kvm_dev_ioctl_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:3355 [inline] > kvm_dev_ioctl+0x137a/0x1a60 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3377 > vfs_ioctl fs/ioctl.c:46 [inline] > file_ioctl fs/ioctl.c:509 [inline] > do_vfs_ioctl+0x107b/0x17d0 fs/ioctl.c:696 > ksys_ioctl+0xab/0xd0 fs/ioctl.c:713 > __do_sys_ioctl fs/ioctl.c:720 [inline] > __se_sys_ioctl fs/ioctl.c:718 [inline] > __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718 > do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x458089 > Code: 6d b7 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 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 > RSP: 002b:00007f69a6d17c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458089 > RDX: 0000000000000000 RSI: 000000000000ae01 RDI: 0000000000000006 > RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 00007f69a6d186d4 > R13: 00000000004c0bcf R14: 00000000004d2890 R15: 00000000ffffffff > Modules linked in: > ---[ end trace c2b508264c762aae ]--- > RIP: 0010:__dentry_path+0x2a5/0xaa0 fs/d_path.c:344 > Code: 00 00 e8 1e 9d 9f ff 48 c7 c7 68 26 81 89 e8 72 c4 14 06 e8 0d 9d 9f ff 48 8b 85 00 ff ff ff 48 8d 78 40 48 89 f8 48 c1 e8 03 <42> 80 3c 38 00 0f 85 b0 07 00 00 48 8b 85 00 ff ff ff 4c 8b 68 40 > RSP: 0018:ffff88808ab5f8a8 EFLAGS: 00010207 > RAX: 0000000000000005 RBX: 0000000000000000 RCX: ffffffff81e27f21 > RDX: 0000000000000000 RSI: ffffffff81e27c43 RDI: 000000000000002f > RBP: ffff88808ab5f9d0 R08: ffff88809edd4280 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000000 R12: ffff88808ab5f9a8 > R13: 0000000000000000 R14: 0000000000000c78 R15: dffffc0000000000 > FS: 00007f69a6d18700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007fec12a1fdb8 CR3: 00000000a1190000 CR4: 00000000001426f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > >
