On Sat, May 26, 2018 at 10:42 AM, syzbot <syzbot+083f3b88782aa3a46bdb@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit: 73fcb1a370c7 Merge branch 'akpm' (patches from Andrew) > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=15b3a827800000 > kernel config: https://syzkaller.appspot.com/x/.config?x=f3b4e30da84ec1ed > dashboard link: https://syzkaller.appspot.com/bug?extid=083f3b88782aa3a46bdb > compiler: gcc (GCC) 8.0.1 20180413 (experimental) > syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1027dbcf800000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=159eff97800000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+083f3b88782aa3a46bdb@xxxxxxxxxxxxxxxxxxxxxxxxx > > random: sshd: uninitialized urandom read (32 bytes read) > random: sshd: uninitialized urandom read (32 bytes read) > random: sshd: uninitialized urandom read (32 bytes read) > ------------[ cut here ]------------ > Bad or missing usercopy whitelist? Kernel memory exposure attempt detected > from SLAB object 'kvm_vcpu' (offset 23192, size 8)! Looks like something else besides the "arch" field is being copied in/out of struct kvm_vcpu? (Also, whoa, 22K struct?) Oh, in looking, I assume it's something in struct vcpu_vmx ? (i.e. this is not fixed by 46515736f8687 ("kvm: whitelist struct kvm_vcpu_arch").) Looks like this is: if (kvm_write_guest_virt_system(&vcpu->arch.emulate_ctxt, vmcs_gva, (void *)&to_vmx(vcpu)->nested.current_vmptr, sizeof(u64), &e)) { ... this is a fixed size, but it looks like it gets down to the copy_*_user() as a variable so automatically whitelisting is happening. :( -Kees > WARNING: CPU: 0 PID: 4554 at mm/usercopy.c:81 usercopy_warn+0xf5/0x120 > mm/usercopy.c:76 > Kernel panic - not syncing: panic_on_warn set ... > > CPU: 0 PID: 4554 Comm: syz-executor726 Not tainted 4.17.0-rc5+ #58 > 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+0x1b9/0x294 lib/dump_stack.c:113 > panic+0x22f/0x4de kernel/panic.c:184 > __warn.cold.8+0x163/0x1b3 kernel/panic.c:536 > report_bug+0x252/0x2d0 lib/bug.c:186 > fixup_bug arch/x86/kernel/traps.c:178 [inline] > do_error_trap+0x1de/0x490 arch/x86/kernel/traps.c:296 > do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315 > invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:992 > RIP: 0010:usercopy_warn+0xf5/0x120 mm/usercopy.c:76 > RSP: 0018:ffff8801ad54f0b0 EFLAGS: 00010286 > RAX: 000000000000007e RBX: ffffffff889d52f0 RCX: ffffffff8160aa5d > RDX: 0000000000000000 RSI: ffffffff8160f711 RDI: ffff8801ad54ec10 > RBP: ffff8801ad54f110 R08: ffff8801d96c8680 R09: 0000000000000006 > R10: ffff8801d96c8680 R11: 0000000000000000 R12: ffffffff87d2fa60 > R13: ffffffff87c19ec0 R14: 0000000000000000 R15: 0000000000000008 > __check_heap_object+0x89/0xb5 mm/slab.c:4440 > check_heap_object mm/usercopy.c:236 [inline] > __check_object_size+0x4c7/0x5d9 mm/usercopy.c:259 > check_object_size include/linux/thread_info.h:108 [inline] > __copy_to_user include/linux/uaccess.h:104 [inline] > __kvm_write_guest_page+0x90/0x140 > arch/x86/kvm/../../../virt/kvm/kvm_main.c:1828 > kvm_vcpu_write_guest_page arch/x86/kvm/../../../virt/kvm/kvm_main.c:1849 > [inline] > kvm_vcpu_write_guest+0x65/0xe0 > arch/x86/kvm/../../../virt/kvm/kvm_main.c:1883 > kvm_write_guest_virt_system+0x8a/0x190 arch/x86/kvm/x86.c:4843 > handle_vmptrst+0x1d2/0x260 arch/x86/kvm/vmx.c:8196 > vmx_handle_exit+0x2c0/0x17b0 arch/x86/kvm/vmx.c:9234 > vcpu_enter_guest+0x13af/0x6060 arch/x86/kvm/x86.c:7503 > vcpu_run arch/x86/kvm/x86.c:7565 [inline] > kvm_arch_vcpu_ioctl_run+0x33e/0x1690 arch/x86/kvm/x86.c:7742 > kvm_vcpu_ioctl+0x79d/0x12e0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2560 > vfs_ioctl fs/ioctl.c:46 [inline] > file_ioctl fs/ioctl.c:500 [inline] > do_vfs_ioctl+0x1cf/0x16a0 fs/ioctl.c:684 > ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701 > __do_sys_ioctl fs/ioctl.c:708 [inline] > __se_sys_ioctl fs/ioctl.c:706 [inline] > __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706 > do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x443039 > RSP: 002b:00007ffc272242b8 EFLAGS: 00000286 ORIG_RAX: 0000000000000010 > RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000443039 > RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005 > RBP: 00000000006cd018 R08: 0000000020000580 R09: 0000000020000580 > R10: 0000000000000000 R11: 0000000000000286 R12: 0000000000404080 > R13: 0000000000404110 R14: 0000000000000000 R15: 0000000000000000 > 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. > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > > syzbot will keep track of this bug report. See: > https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with > syzbot. > syzbot can test patches for this bug, for details see: > https://goo.gl/tpsmEJ#testing-patches -- Kees Cook Pixel Security
