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Subject[PATCH 4.4 002/266] KVM: fail KVM_SET_VCPU_EVENTS with invalid exception number
Date
commit 78e546c824fa8f96d323b7edd6f5cad5b74af057 upstream

This cannot be returned by KVM_GET_VCPU_EVENTS, so it is okay to return
EINVAL. It causes a WARN from exception_type:

WARNING: CPU: 3 PID: 16732 at arch/x86/kvm/x86.c:345 exception_type+0x49/0x50 [kvm]()
CPU: 3 PID: 16732 Comm: a.out Tainted: G W 4.4.6-300.fc23.x86_64 #1
Hardware name: LENOVO 2325F51/2325F51, BIOS G2ET32WW (1.12 ) 05/30/2012
0000000000000286 000000006308a48b ffff8800bec7fcf8 ffffffff813b542e
0000000000000000 ffffffffa0966496 ffff8800bec7fd30 ffffffff810a40f2
ffff8800552a8000 0000000000000000 00000000002c267c 0000000000000001
Call Trace:
[<ffffffff813b542e>] dump_stack+0x63/0x85
[<ffffffff810a40f2>] warn_slowpath_common+0x82/0xc0
[<ffffffff810a423a>] warn_slowpath_null+0x1a/0x20
[<ffffffffa0924809>] exception_type+0x49/0x50 [kvm]
[<ffffffffa0934622>] kvm_arch_vcpu_ioctl_run+0x10a2/0x14e0 [kvm]
[<ffffffffa091c04d>] kvm_vcpu_ioctl+0x33d/0x620 [kvm]
[<ffffffff81241248>] do_vfs_ioctl+0x298/0x480
[<ffffffff812414a9>] SyS_ioctl+0x79/0x90
[<ffffffff817a04ee>] entry_SYSCALL_64_fastpath+0x12/0x71
---[ end trace b1a0391266848f50 ]---

Testcase (beautified/reduced from syzkaller output):

#include <unistd.h>
#include <sys/syscall.h>
#include <string.h>
#include <stdint.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/kvm.h>

long r[31];

int main()
{
memset(r, -1, sizeof(r));
r[2] = open("/dev/kvm", O_RDONLY);
r[3] = ioctl(r[2], KVM_CREATE_VM, 0);
r[7] = ioctl(r[3], KVM_CREATE_VCPU, 0);

struct kvm_vcpu_events ve = {
.exception.injected = 1,
.exception.nr = 0xd4
};
r[27] = ioctl(r[7], KVM_SET_VCPU_EVENTS, &ve);
r[30] = ioctl(r[7], KVM_RUN, 0);
return 0;
}

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Zubin Mithra <zsm@chromium.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kvm/x86.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2972,6 +2972,10 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_e
| KVM_VCPUEVENT_VALID_SMM))
return -EINVAL;

+ if (events->exception.injected &&
+ (events->exception.nr > 31 || events->exception.nr == NMI_VECTOR))
+ return -EINVAL;
+
/* INITs are latched while in SMM */
if (events->flags & KVM_VCPUEVENT_VALID_SMM &&
(events->smi.smm || events->smi.pending) &&

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