This is a note to let you know that I've just added the patch titled
KVM: x86: Fix far-jump to non-canonical check
to the 3.17-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-far-jump-to-non-canonical-check.patch
and it can be found in the queue-3.17 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7e46dddd6f6cd5dbf3c7bd04a7e75d19475ac9f2 Mon Sep 17 00:00:00 2001
From: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
Date: Tue, 28 Oct 2014 00:03:43 +0200
Subject: KVM: x86: Fix far-jump to non-canonical check
From: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
commit 7e46dddd6f6cd5dbf3c7bd04a7e75d19475ac9f2 upstream.
Commit d1442d85cc30 ("KVM: x86: Handle errors when RIP is set during far
jumps") introduced a bug that caused the fix to be incomplete. Due to
incorrect evaluation, far jump to segment with L bit cleared (i.e., 32-bit
segment) and RIP with any of the high bits set (i.e, RIP[63:32] != 0) set may
not trigger #GP. As we know, this imposes a security problem.
In addition, the condition for two warnings was incorrect.
Fixes: d1442d85cc30ea75f7d399474ca738e0bc96f715
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
[Add #ifdef CONFIG_X86_64 to avoid complaints of undefined behavior. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/emulate.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -573,12 +573,14 @@ static inline int assign_eip_far(struct
case 4:
ctxt->_eip = (u32)dst;
break;
+#ifdef CONFIG_X86_64
case 8:
if ((cs_l && is_noncanonical_address(dst)) ||
- (!cs_l && (dst & ~(u32)-1)))
+ (!cs_l && (dst >> 32) != 0))
return emulate_gp(ctxt, 0);
ctxt->_eip = dst;
break;
+#endif
default:
WARN(1, "unsupported eip assignment size\n");
}
@@ -2026,7 +2028,7 @@ static int em_jmp_far(struct x86_emulate
rc = assign_eip_far(ctxt, ctxt->src.val, new_desc.l);
if (rc != X86EMUL_CONTINUE) {
- WARN_ON(!ctxt->mode != X86EMUL_MODE_PROT64);
+ WARN_ON(ctxt->mode != X86EMUL_MODE_PROT64);
/* assigning eip failed; restore the old cs */
ops->set_segment(ctxt, old_sel, &old_desc, 0, VCPU_SREG_CS);
return rc;
@@ -2123,7 +2125,7 @@ static int em_ret_far(struct x86_emulate
return rc;
rc = assign_eip_far(ctxt, eip, new_desc.l);
if (rc != X86EMUL_CONTINUE) {
- WARN_ON(!ctxt->mode != X86EMUL_MODE_PROT64);
+ WARN_ON(ctxt->mode != X86EMUL_MODE_PROT64);
ops->set_segment(ctxt, old_cs, &old_desc, 0, VCPU_SREG_CS);
}
return rc;
Patches currently in stable-queue which might be from namit@xxxxxxxxxxxxxxxxx are
queue-3.17/kvm-x86-fix-far-jump-to-non-canonical-check.patch
queue-3.17/kvm-x86-handle-errors-when-rip-is-set-during-far-jumps.patch
queue-3.17/kvm-x86-emulator-fixes-for-eip-canonical-checks-on-near-branches.patch
queue-3.17/kvm-x86-emulator-does-not-decode-clflush-well.patch
queue-3.17/kvm-x86-fix-wrong-masking-on-relative-jump-call.patch
queue-3.17/kvm-x86-prefetch-and-hint_nop-should-have-srcmem-flag.patch
queue-3.17/kvm-x86-decoding-guest-instructions-which-cross-page-boundary-may-fail.patch
queue-3.17/kvm-x86-check-non-canonical-addresses-upon-wrmsr.patch
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