Patch "KVM: VMX: Fix rflags cache during vCPU reset" has been added to the 4.14-stable tree
Subsystems (3)
This is a note to let you know that I've just added the patch titled
KVM: VMX: Fix rflags cache during vCPU reset
to the 4.14-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-vmx-fix-rflags-cache-during-vcpu-reset.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.
Quoted 1 line
From foo@baz Thu Feb 1 13:45:42 CET 2018
From: Wanpeng Li <[email protected]>
Date: Mon, 20 Nov 2017 14:52:21 -0800
Subject: KVM: VMX: Fix rflags cache during vCPU reset
From: Wanpeng Li <[email protected]>
[ Upstream commit c37c28730bb031cc8a44a130c2555c0f3efbe2d0 ]
Reported by syzkaller:
*** Guest State ***
CR0: actual=0x0000000080010031, shadow=0x0000000060000010, gh_mask=fffffffffffffff7
CR4: actual=0x0000000000002061, shadow=0x0000000000000000, gh_mask=ffffffffffffe8f1 CR3 = 0x000000002081e000
RSP = 0x000000000000fffa RIP = 0x0000000000000000
RFLAGS=0x00023000 DR7 = 0x00000000000000
^^^^^^^^^^
------------[ cut here ]------------
WARNING: CPU: 6 PID: 24431 at /home/kernel/linux/arch/x86/kvm//x86.c:7302 kvm_arch_vcpu_ioctl_run+0x651/0x2ea0 [kvm]
CPU: 6 PID: 24431 Comm: reprotest Tainted: G W OE 4.14.0+ #26
RIP: 0010:kvm_arch_vcpu_ioctl_run+0x651/0x2ea0 [kvm]
RSP: 0018:ffff880291d179e0 EFLAGS: 00010202
Call Trace:
kvm_vcpu_ioctl+0x479/0x880 [kvm]
do_vfs_ioctl+0x142/0x9a0
SyS_ioctl+0x74/0x80
entry_SYSCALL_64_fastpath+0x23/0x9aThe failed vmentry is triggered by the following beautified testcase:
#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()
{
struct kvm_debugregs dr = { 0 };
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_guest_debug debug = {
.control = 0xf0403,
.arch = {
.debugreg[6] = 0x2,
.debugreg[7] = 0x2
}
};
ioctl(r[4], KVM_SET_GUEST_DEBUG, &debug);
ioctl(r[4], KVM_RUN, 0);
}which testcase tries to setup the processor specific debug registers and configure vCPU for handling guest debug events through KVM_SET_GUEST_DEBUG. The KVM_SET_GUEST_DEBUG ioctl will get and set rflags in order to set TF bit if single step is needed. All regs' caches are reset to avail and GUEST_RFLAGS vmcs field is reset to 0x2 during vCPU reset. However, the cache of rflags is not reset during vCPU reset. The function vmx_get_rflags() returns an unreset rflags cache value since the cache is marked avail, it is 0 after boot. Vmentry fails if the rflags reserved bit 1 is 0.
This patch fixes it by resetting both the GUEST_RFLAGS vmcs field and its cache to 0x2 during vCPU reset.
--- arch/x86/kvm/vmx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
arch/x86/kvm/vmx.c +1 -1
@@ -5608,7 +5608,7 @@ static void vmx_vcpu_reset(struct kvm_vcvmcs_write64 (GUEST_IA32_DEBUGCTL ,0 ); } -vmcs_writel (GUEST_RFLAGS ,0x02 ); +kvm_set_rflags (vcpu,X86_EFLAGS_FIXED );kvm_rip_write (vcpu,0xfff0 );vmcs_writel (GUEST_GDTR_BASE ,0 );
Patches currently in stable-queue which might be from [email protected] are
queue-4.14/kvm-x86-don-t-re-execute-instruction-when-not-passing-cr2-value.patch queue-4.14/kvm-x86-ioapic-preserve-read-only-values-in-the-redirection-table.patch queue-4.14/kvm-nvmx-fix-mmu-context-after-vmlaunch-vmresume-failure.patch queue-4.14/kvm-vmx-fix-rflags-cache-during-vcpu-reset.patch queue-4.14/kvm-x86-fix-operand-address-size-during-instruction-decoding.patch queue-4.14/kvm-x86-emulator-return-to-user-mode-on-l1-cpl-0-emulation-failure.patch queue-4.14/kvm-nvmx-nsvm-don-t-intercept-ud-when-running-l2.patch queue-4.14/kvm-x86-fix-softlockup-when-get-the-current-kvmclock.patch queue-4.14/kvm-x86-ioapic-clear-remote-irr-when-entry-is-switched-to-edge-triggered.patch