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From 83f00ab9a7c03e9f1410727d985b7fe9473002e1 Mon Sep 17 00:00:00 2001
From: Wanpeng Li <wanpengli@tencent.com>
Date: Tue, 20 Nov 2018 16:34:18 +0800
Subject: [PATCH] KVM: X86: Fix scan ioapic use-before-initialization
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
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;Backport
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.
CVE: CVE-2018-19407
Upstream-Status: Backport
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
---
arch/x86/kvm/x86.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7c4d02dba110..f24329659bea 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6885,7 +6885,8 @@ static void vcpu_scan_ioapic(struct kvm_vcpu *vcpu)
else {
if (kvm_x86_ops->sync_pir_to_irr && vcpu->arch.apicv_active)
kvm_x86_ops->sync_pir_to_irr(vcpu);
- kvm_ioapic_scan_entry(vcpu, vcpu->arch.ioapic_handled_vectors);
+ if (ioapic_in_kernel(vcpu->kvm))
+ kvm_ioapic_scan_entry(vcpu, vcpu->arch.ioapic_handled_vectors);
}
bitmap_or((ulong *)eoi_exit_bitmap, vcpu->arch.ioapic_handled_vectors,
vcpu_to_synic(vcpu)->vec_bitmap, 256);
--
2.19.2
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