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%3Ba=su...

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@vger.kernel.org know about it.

From d73235d17ba63b53dc0e1051dbc10a1f1be91b71 Mon Sep 17 00:00:00 2001

From: Wanpeng Li wanpeng.li@hotmail.com Date: Thu, 7 Dec 2017 00:30:08 -0800 Subject: KVM: X86: Fix load RFLAGS w/o the fixed bit MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

From: Wanpeng Li wanpeng.li@hotmail.com

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, &regs); 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@google.com Reviewed-by: David Hildenbrand david@redhat.com Reviewed-by: Quan Xu quan.xu0@gmail.com Cc: Paolo Bonzini pbonzini@redhat.com Cc: Radim Krčmář rkrcmar@redhat.com Cc: Jim Mattson jmattson@google.com Signed-off-by: Wanpeng Li wanpeng.li@hotmail.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- 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@hotmail.com are

queue-4.4/kvm-x86-fix-load-rflags-w-o-the-fixed-bit.patch