Fix CVE-2018-10853 (rhbz 1589890 1589892)

kernel.spec

@@ -668,6 +668,9 @@ Patch513: ext4-correctly-handle-a-zero-length-xattr-with-a-non.patch
 # https://www.spinics.net/lists/kernel/msg2818652.html applies cleanly to 4.17
 Patch514: libata-Drop-SanDisk-SD7UB3Q-G1001-NOLPM-quirk.patch
 
+# CVE-2018-10853 rhbz 1589890 1589892
+Patch515: kvm-x86-Check-CPL-in-segmented_write_std.patch
+
 # END OF PATCH DEFINITIONS
 
 %endif
@@ -1918,6 +1921,9 @@ fi
 #
 #
 %changelog
+* Mon Jun 11 2018 Justin M. Forbes <jforbes@fedoraproject.org>
+- Fix CVE-2018-10853 (rhbz 1589890 1589892)
+
 * Tue Jun 05 2018 Jeremy Cline <jeremy@jcline.org>
 - Enable CONFIG_SCSI_DH on s390x (rhbz 1586189)
 

kvm-x86-Check-CPL-in-segmented_write_std.patch

@@ -0,0 +1,43 @@
+From patchwork Tue Jun  5 20:04:16 2018
+Content-Type: text/plain; charset="utf-8"
+MIME-Version: 1.0
+Content-Transfer-Encoding: 7bit
+Subject: kvm: x86: Check CPL in segmented_write_std
+From: Bandan Das <bsd@redhat.com>
+X-Patchwork-Id: 10449159
+Message-Id: <jpgtvqhuhj3.fsf@linux.bootlegged.copy>
+To: kvm@vger.kernel.org
+Cc: Paolo Bonzini <pbonzini@redhat.com>,
+ Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
+ Andy Lutomirski <luto@kernel.org>
+Date: Tue, 05 Jun 2018 16:04:16 -0400
+
+Certain instructions such as sgdt/sidt call segmented_write_std that
+doesn't propagate access correctly. As such, during userspace induced
+exception, the guest can incorrectly assume that the exception
+happened in the kernel and panic. The emulated write function
+segmented_write does seem to check access correctly.
+
+Reported-by: Andy Lutomirski <luto@kernel.org>
+Signed-off-by: Bandan Das <bsd@redhat.com>
+---
+ arch/x86/kvm/x86.c | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
+index 71e7cda6d014..871265f6a35f 100644
+--- a/arch/x86/kvm/x86.c
++++ b/arch/x86/kvm/x86.c
+@@ -4824,10 +4824,11 @@ int kvm_write_guest_virt_system(struct x86_emulate_ctxt *ctxt,
+ 	struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);
+ 	void *data = val;
+ 	int r = X86EMUL_CONTINUE;
++	u32 access = (kvm_x86_ops->get_cpl(vcpu) == 3) ? PFERR_USER_MASK : 0;
+ 
+ 	while (bytes) {
+ 		gpa_t gpa =  vcpu->arch.walk_mmu->gva_to_gpa(vcpu, addr,
+-							     PFERR_WRITE_MASK,
++							     access | PFERR_WRITE_MASK,
+ 							     exception);
+ 		unsigned offset = addr & (PAGE_SIZE-1);
+ 		unsigned towrite = min(bytes, (unsigned)PAGE_SIZE - offset);