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SubjectRe: [PATCH 3.13 106/162] KVM: x86: Fix far-jump to non-canonical check
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On Thu, Nov 6, 2014 at 2:36 PM, Kamal Mostafa <kamal@canonical.com> wrote:
> 3.13.11.11 -stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Nadav Amit <namit@cs.technion.ac.il>
>
> 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@oracle.com>
> Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
> [Add #ifdef CONFIG_X86_64 to avoid complaints of undefined behavior. - Paolo]
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> [ kamal: backport to 3.13-stable: omitted WARN_ON fixes (not in 3.13) ]
> Signed-off-by: Kamal Mostafa <kamal@canonical.com>
> ---
> arch/x86/kvm/emulate.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index a440bea..4ae37e7 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -581,12 +581,14 @@ static inline int assign_eip_far(struct x86_emulate_ctxt *ctxt, ulong dst,
> 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");
> }
> --
> 1.9.1
>
> --
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Hi.

Should the WARN_ON fixes have been included as well in 3.13.11.11?

WARN_ON hunks were added with the backport of "KVM: x86: Handle errors
when RIP is set during far jumps" in 3.13.11.11 commit
b8ba339d86fb627d54fea929492114d45f6835c2.

Cheers,
Vinson


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