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; }
