From: Wanpeng Li wanpengli@tencent.com
commit e97f852fd4561e77721bb9a4e0ea9d98305b1e93 upstream.
Reported by syzkaller:
BUG: unable to handle kernel NULL pointer dereference at 00000000000001c8 PGD 80000003ec4da067 P4D 80000003ec4da067 PUD 3f7bfa067 PMD 0 Oops: 0000 [#1] PREEMPT SMP PTI CPU: 7 PID: 5059 Comm: debug Tainted: G OE 4.19.0-rc5 #16 RIP: 0010:__lock_acquire+0x1a6/0x1990 Call Trace: lock_acquire+0xdb/0x210 _raw_spin_lock+0x38/0x70 kvm_ioapic_scan_entry+0x3e/0x110 [kvm] vcpu_enter_guest+0x167e/0x1910 [kvm] kvm_arch_vcpu_ioctl_run+0x35c/0x610 [kvm] kvm_vcpu_ioctl+0x3e9/0x6d0 [kvm] do_vfs_ioctl+0xa5/0x690 ksys_ioctl+0x6d/0x80 __x64_sys_ioctl+0x1a/0x20 do_syscall_64+0x83/0x6e0 entry_SYSCALL_64_after_hwframe+0x49/0xbe
The reason is that the testcase writes hyperv synic HV_X64_MSR_SINT6 msr and triggers scan ioapic logic to load synic vectors into EOI exit bitmap. However, irqchip is not initialized by this simple testcase, ioapic/apic objects should not be accessed. This can be triggered by the following program:
#define _GNU_SOURCE
#include <endian.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/syscall.h> #include <sys/types.h> #include <unistd.h>
uint64_t r[3] = {0xffffffffffffffff, 0xffffffffffffffff, 0xffffffffffffffff};
int main(void) { syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0); long res = 0; memcpy((void*)0x20000040, "/dev/kvm", 9); res = syscall(__NR_openat, 0xffffffffffffff9c, 0x20000040, 0, 0); if (res != -1) r[0] = res; res = syscall(__NR_ioctl, r[0], 0xae01, 0); if (res != -1) r[1] = res; res = syscall(__NR_ioctl, r[1], 0xae41, 0); if (res != -1) r[2] = res; memcpy( (void*)0x20000080, "\x01\x00\x00\x00\x00\x5b\x61\xbb\x96\x00\x00\x40\x00\x00\x00\x00\x01\x00" "\x08\x00\x00\x00\x00\x00\x0b\x77\xd1\x78\x4d\xd8\x3a\xed\xb1\x5c\x2e\x43" "\xaa\x43\x39\xd6\xff\xf5\xf0\xa8\x98\xf2\x3e\x37\x29\x89\xde\x88\xc6\x33" "\xfc\x2a\xdb\xb7\xe1\x4c\xac\x28\x61\x7b\x9c\xa9\xbc\x0d\xa0\x63\xfe\xfe" "\xe8\x75\xde\xdd\x19\x38\xdc\x34\xf5\xec\x05\xfd\xeb\x5d\xed\x2e\xaf\x22" "\xfa\xab\xb7\xe4\x42\x67\xd0\xaf\x06\x1c\x6a\x35\x67\x10\x55\xcb", 106); syscall(__NR_ioctl, r[2], 0x4008ae89, 0x20000080); syscall(__NR_ioctl, r[2], 0xae80, 0); return 0; }
This patch fixes it by bailing out scan ioapic if ioapic is not initialized in kernel.
Reported-by: Wei Wu ww9210@gmail.com Cc: Paolo Bonzini pbonzini@redhat.com Cc: Radim Krčmář rkrcmar@redhat.com Cc: Wei Wu ww9210@gmail.com Signed-off-by: Wanpeng Li wanpengli@tencent.com Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com [ Srivatsa: Adjusted the context for 4.4.y ] Signed-off-by: Srivatsa S. Bhat (VMware) srivatsa@csail.mit.edu Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kvm/x86.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6409,7 +6409,8 @@ static void vcpu_scan_ioapic(struct kvm_ kvm_scan_ioapic_routes(vcpu, vcpu->arch.eoi_exit_bitmap); else { kvm_x86_ops->sync_pir_to_irr(vcpu); - kvm_ioapic_scan_entry(vcpu, vcpu->arch.eoi_exit_bitmap); + if (ioapic_in_kernel(vcpu->kvm)) + kvm_ioapic_scan_entry(vcpu, vcpu->arch.eoi_exit_bitmap); } kvm_x86_ops->load_eoi_exitmap(vcpu); }