104 lines
3.5 KiB
Diff
104 lines
3.5 KiB
Diff
From: Wanpeng Li <kernellwp@gmail.com>
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Date: Tue, 27 Nov 2018 14:01:04 -0500
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Subject: [PATCH] KVM: X86: Fix scan ioapic use-before-initialization
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Reported by syzkaller:
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BUG: unable to handle kernel NULL pointer dereference at 00000000000001c8
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PGD 80000003ec4da067 P4D 80000003ec4da067 PUD 3f7bfa067 PMD 0
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Oops: 0000 [#1] PREEMPT SMP PTI
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CPU: 7 PID: 5059 Comm: debug Tainted: G OE 4.19.0-rc5 #16
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RIP: 0010:__lock_acquire+0x1a6/0x1990
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Call Trace:
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lock_acquire+0xdb/0x210
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_raw_spin_lock+0x38/0x70
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kvm_ioapic_scan_entry+0x3e/0x110 [kvm]
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vcpu_enter_guest+0x167e/0x1910 [kvm]
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kvm_arch_vcpu_ioctl_run+0x35c/0x610 [kvm]
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kvm_vcpu_ioctl+0x3e9/0x6d0 [kvm]
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do_vfs_ioctl+0xa5/0x690
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ksys_ioctl+0x6d/0x80
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__x64_sys_ioctl+0x1a/0x20
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do_syscall_64+0x83/0x6e0
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entry_SYSCALL_64_after_hwframe+0x49/0xbe
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The reason is that the testcase writes hyperv synic HV_X64_MSR_SINT6 msr
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and triggers scan ioapic logic to load synic vectors into EOI exit bitmap.
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However, irqchip is not initialized by this simple testcase, ioapic/apic
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objects should not be accessed.
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This can be triggered by the following program:
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#define _GNU_SOURCE
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#include <endian.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/syscall.h>
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#include <sys/types.h>
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#include <unistd.h>
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uint64_t r[3] = {0xffffffffffffffff, 0xffffffffffffffff, 0xffffffffffffffff};
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int main(void)
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{
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syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0);
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long res = 0;
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memcpy((void*)0x20000040, "/dev/kvm", 9);
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res = syscall(__NR_openat, 0xffffffffffffff9c, 0x20000040, 0, 0);
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if (res != -1)
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r[0] = res;
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res = syscall(__NR_ioctl, r[0], 0xae01, 0);
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if (res != -1)
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r[1] = res;
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res = syscall(__NR_ioctl, r[1], 0xae41, 0);
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if (res != -1)
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r[2] = res;
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memcpy(
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(void*)0x20000080,
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"\x01\x00\x00\x00\x00\x5b\x61\xbb\x96\x00\x00\x40\x00\x00\x00\x00\x01\x00"
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"\x08\x00\x00\x00\x00\x00\x0b\x77\xd1\x78\x4d\xd8\x3a\xed\xb1\x5c\x2e\x43"
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"\xaa\x43\x39\xd6\xff\xf5\xf0\xa8\x98\xf2\x3e\x37\x29\x89\xde\x88\xc6\x33"
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"\xfc\x2a\xdb\xb7\xe1\x4c\xac\x28\x61\x7b\x9c\xa9\xbc\x0d\xa0\x63\xfe\xfe"
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"\xe8\x75\xde\xdd\x19\x38\xdc\x34\xf5\xec\x05\xfd\xeb\x5d\xed\x2e\xaf\x22"
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"\xfa\xab\xb7\xe4\x42\x67\xd0\xaf\x06\x1c\x6a\x35\x67\x10\x55\xcb",
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106);
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syscall(__NR_ioctl, r[2], 0x4008ae89, 0x20000080);
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syscall(__NR_ioctl, r[2], 0xae80, 0);
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return 0;
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}
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This patch fixes it by bailing out scan ioapic if ioapic is not initialized in
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kernel.
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Reported-by: Wei Wu <ww9210@gmail.com>
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Cc: Paolo Bonzini <pbonzini@redhat.com>
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Cc: Radim Krčmář <rkrcmar@redhat.com>
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Cc: Wei Wu <ww9210@gmail.com>
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Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
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Signed-off-by: Jeremy Cline <jcline@redhat.com>
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---
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arch/x86/kvm/x86.c | 3 ++-
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1 file changed, 2 insertions(+), 1 deletion(-)
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diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
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index ca717737347e..89694cbf84cf 100644
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--- a/arch/x86/kvm/x86.c
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+++ b/arch/x86/kvm/x86.c
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@@ -7313,7 +7313,8 @@ static void vcpu_scan_ioapic(struct kvm_vcpu *vcpu)
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else {
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if (vcpu->arch.apicv_active)
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kvm_x86_ops->sync_pir_to_irr(vcpu);
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- kvm_ioapic_scan_entry(vcpu, vcpu->arch.ioapic_handled_vectors);
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+ if (ioapic_in_kernel(vcpu->kvm))
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+ kvm_ioapic_scan_entry(vcpu, vcpu->arch.ioapic_handled_vectors);
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}
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if (is_guest_mode(vcpu))
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--
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2.19.1
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