On Wed, Aug 9, 2017 at 7:09 PM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: > -non-existent email address > > On Wed, Aug 9, 2017 at 7:07 PM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: >> Hello, >> >> syzkaller fuzzer has hit the following WARNING in kvm_arch_vcpu_ioctl_run. >> This is easily reproducible and reproducer is attached at the bottom. >> The report is on upstream commit >> 26c5cebfdb6ca799186f1e56be7d6f2480c5012c. This requires setting >> kvm-intel.unrestricted_guest=0 on the machine, with >> unrestricted_guest=1 the WARNING does not happen. Output of the >> program is: >> >> ret1=0 exit_reason=17 suberror=1 >> ret2=0 exit_reason=8 suberror=65530 >> >> >> WARNING: CPU: 1 PID: 2850 at arch/x86/kvm/x86.c:7223 >> kvm_arch_vcpu_ioctl_run+0x213/0x5870 arch/x86/kvm/x86.c:7223 >> CPU: 1 PID: 2850 Comm: a.out Not tainted 4.13.0-rc3+ #445 >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 >> Call Trace: >> __dump_stack lib/dump_stack.c:16 [inline] >> dump_stack+0x194/0x257 lib/dump_stack.c:52 >> panic+0x1e4/0x417 kernel/panic.c:180 >> __warn+0x1c4/0x1d9 kernel/panic.c:541 >> report_bug+0x211/0x2d0 lib/bug.c:183 >> fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:190 >> do_trap_no_signal arch/x86/kernel/traps.c:224 [inline] >> do_trap+0x260/0x390 arch/x86/kernel/traps.c:273 >> do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:310 >> do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:323 >> invalid_op+0x1e/0x30 arch/x86/entry/entry_64.S:846 >> RIP: 0010:kvm_arch_vcpu_ioctl_run+0x213/0x5870 arch/x86/kvm/x86.c:7222 >> RSP: 0018:ffff8800627cf670 EFLAGS: 00010297 >> RAX: ffff880066c44480 RBX: ffff88006b07f000 RCX: ffff880067d0845c >> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff880067d08260 >> RBP: ffff8800627cfa40 R08: 0000000000000001 R09: 0000000000000000 >> R10: ffff8800627cfa58 R11: 0000000000000000 R12: 0000000000000001 >> R13: 0000000000000000 R14: ffff88006b934880 R15: ffff880067d08040 >> kvm_vcpu_ioctl+0x64c/0x1010 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2592 >> vfs_ioctl fs/ioctl.c:45 [inline] >> do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:685 >> SYSC_ioctl fs/ioctl.c:700 [inline] >> SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691 >> entry_SYSCALL_64_fastpath+0x1f/0xbe >> RIP: 0033:0x44ccc9 >> RSP: 002b:00007f9ecbc37db8 EFLAGS: 00000297 ORIG_RAX: 0000000000000010 >> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000044ccc9 >> RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005 >> RBP: 0000000000000082 R08: 00007f9ecbc38700 R09: 0000000000000000 >> R10: 00007f9ecbc38700 R11: 0000000000000297 R12: 0000000000000000 >> R13: 0000000000000000 R14: 00007f9ecbc389c0 R15: 00007f9ecbc38700 >> >> >> >> // autogenerated by syzkaller (http://github.com/google/syzkaller) >> #define _GNU_SOURCE >> #include <pthread.h> >> #include <stdio.h> >> #include <stdlib.h> >> #include <string.h> >> #include <sys/wait.h> >> #include <sys/types.h> >> #include <sys/stat.h> >> #include <sys/mman.h> >> #include <fcntl.h> >> #include <unistd.h> >> #include <linux/kvm.h> >> #include <stdio.h> >> >> int kvmcpu; >> struct kvm_run *run; >> >> void* thr(void* arg) >> { >> int res; >> res = ioctl(kvmcpu, KVM_RUN, 0); >> printf("ret1=%d exit_reason=%d suberror=%d\n", >> res, run->exit_reason, run->internal.suberror); >> return 0; >> } >> >> void test() >> { >> int i, kvm, kvmvm; >> pthread_t th[4]; >> >> kvm = open("/dev/kvm", O_RDWR); >> kvmvm = ioctl(kvm, KVM_CREATE_VM, 0); >> kvmcpu = ioctl(kvmvm, KVM_CREATE_VCPU, 0); >> run = (struct kvm_run*)mmap(0, 4096, PROT_READ|PROT_WRITE, >> MAP_SHARED, kvmcpu, 0); >> srand(getpid()); >> for (i = 0; i < 4; i++) { >> pthread_create(&th[i], 0, thr, 0); >> usleep(rand() % 10000); >> } >> for (i = 0; i < 4; i++) >> pthread_join(th[i], 0); >> } >> >> int main() >> { >> for (;;) { >> int pid = fork(); >> if (pid < 0) >> exit(1); >> if (pid == 0) { >> test(); >> exit(0); >> } >> int status; >> while (waitpid(pid, &status, __WALL) != pid) {} >> } >> return 0; >> } For the record, James suggested the following patch, but it does _not_ help: diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 6c97c82814c4..21391c9241bc 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5383,6 +5383,7 @@ static int handle_emulation_failure(struct kvm_vcpu *vcpu) vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION; vcpu->run->internal.ndata = 0; + vcpu->arch.pio.count = 0; r = EMULATE_FAIL; } kvm_queue_exception(vcpu, UD_VECTOR);
