This is a note to let you know that I've just added the patch titled
KVM: X86: Fix load RFLAGS w/o the fixed bit
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-x86-fix-load-rflags-w-o-the-fixed-bit.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From d73235d17ba63b53dc0e1051dbc10a1f1be91b71 Mon Sep 17 00:00:00 2001
From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
Date: Thu, 7 Dec 2017 00:30:08 -0800
Subject: KVM: X86: Fix load RFLAGS w/o the fixed bit
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From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
commit d73235d17ba63b53dc0e1051dbc10a1f1be91b71 upstream.
*** Guest State ***
CR0: actual=0x0000000000000030, shadow=0x0000000060000010, gh_mask=fffffffffffffff7
CR4: actual=0x0000000000002050, shadow=0x0000000000000000, gh_mask=ffffffffffffe871
CR3 = 0x00000000fffbc000
RSP = 0x0000000000000000 RIP = 0x0000000000000000
RFLAGS=0x00000000 DR7 = 0x0000000000000400
^^^^^^^^^^
The failed vmentry is triggered by the following testcase when ept=Y:
#include <unistd.h>
#include <sys/syscall.h>
#include <string.h>
#include <stdint.h>
#include <linux/kvm.h>
#include <fcntl.h>
#include <sys/ioctl.h>
long r[5];
int main()
{
r[2] = open("/dev/kvm", O_RDONLY);
r[3] = ioctl(r[2], KVM_CREATE_VM, 0);
r[4] = ioctl(r[3], KVM_CREATE_VCPU, 7);
struct kvm_regs regs = {
.rflags = 0,
};
ioctl(r[4], KVM_SET_REGS, ®s);
ioctl(r[4], KVM_RUN, 0);
}
X86 RFLAGS bit 1 is fixed set, userspace can simply clearing bit 1
of RFLAGS with KVM_SET_REGS ioctl which results in vmentry fails.
This patch fixes it by oring X86_EFLAGS_FIXED during ioctl.
Suggested-by: Jim Mattson <jmattson@xxxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Quan Xu <quan.xu0@xxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Cc: Jim Mattson <jmattson@xxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/x86.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6941,7 +6941,7 @@ int kvm_arch_vcpu_ioctl_set_regs(struct
#endif
kvm_rip_write(vcpu, regs->rip);
- kvm_set_rflags(vcpu, regs->rflags);
+ kvm_set_rflags(vcpu, regs->rflags | X86_EFLAGS_FIXED);
vcpu->arch.exception.pending = false;
Patches currently in stable-queue which might be from wanpeng.li@xxxxxxxxxxx are
queue-4.4/kvm-x86-fix-load-rflags-w-o-the-fixed-bit.patch