Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754769AbbKWNOO (ORCPT ); Mon, 23 Nov 2015 08:14:14 -0500 Received: from mx2.suse.de ([195.135.220.15]:59800 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754714AbbKWNMq (ORCPT ); Mon, 23 Nov 2015 08:12:46 -0500 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Nadav Amit , Paolo Bonzini , Jiri Slaby Subject: [PATCH 3.12 68/72] KVM: x86: Fix far-jump to non-canonical check Date: Mon, 23 Nov 2015 14:12:29 +0100 Message-Id: X-Mailer: git-send-email 2.6.3 In-Reply-To: <09f041d02b9d5407d544d6fd5a9026072c44956f.1448283890.git.jslaby@suse.cz> References: <09f041d02b9d5407d544d6fd5a9026072c44956f.1448283890.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2612 Lines: 72 From: Nadav Amit 3.12-stable review patch. If anyone has any objections, please let me know. =============== 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 Signed-off-by: Nadav Amit [Add #ifdef CONFIG_X86_64 to avoid complaints of undefined behavior. - Paolo] Signed-off-by: Paolo Bonzini Signed-off-by: Jiri Slaby --- arch/x86/kvm/emulate.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 8216f484398f..ffae11d0754a 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -582,12 +582,14 @@ 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"); } @@ -2000,7 +2002,7 @@ static int em_jmp_far(struct x86_emulate_ctxt *ctxt) 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; @@ -2084,7 +2086,7 @@ static int em_ret_far(struct x86_emulate_ctxt *ctxt) 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; -- 2.6.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/