From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Thu, 18 Aug 2016 16:12:08 +0200 (CEST) Received: from mail.linuxfoundation.org ([140.211.169.12]:53992 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S23993204AbcHROL7bGkiI (ORCPT ); Thu, 18 Aug 2016 16:11:59 +0200 Received: from localhost (pes75-3-78-192-101-3.fbxo.proxad.net [78.192.101.3]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 4905678D; Thu, 18 Aug 2016 14:11:51 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, James Hogan , Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Ralf Baechle , linux-mips@linux-mips.org, kvm@vger.kernel.org Subject: [PATCH 4.7 085/186] MIPS: KVM: Fix mapped fault broken commpage handling Date: Thu, 18 Aug 2016 15:58:22 +0200 Message-Id: <20160818135935.761248419@linuxfoundation.org> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20160818135932.219369981@linuxfoundation.org> References: <20160818135932.219369981@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 54647 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: gregkh@linuxfoundation.org Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips 4.7-stable review patch. If anyone has any objections, please let me know. ------------------ From: James Hogan commit c604cffa93478f8888bec62b23d6073dad03d43a upstream. kvm_mips_handle_mapped_seg_tlb_fault() appears to map the guest page at virtual address 0 to PFN 0 if the guest has created its own mapping there. The intention is unclear, but it may have been an attempt to protect the zero page from being mapped to anything but the comm page in code paths you wouldn't expect from genuine commpage accesses (guest kernel mode cache instructions on that address, hitting trapping instructions when executing from that address with a coincidental TLB eviction during the KVM handling, and guest user mode accesses to that address). Fix this to check for mappings exactly at KVM_GUEST_COMMPAGE_ADDR (it may not be at address 0 since commit 42aa12e74e91 ("MIPS: KVM: Move commpage so 0x0 is unmapped")), and set the corresponding EntryLo to be interpreted as 0 (invalid). Fixes: 858dd5d45733 ("KVM/MIPS32: MMU/TLB operations for the Guest.") Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org Cc: # 3.10.x- Signed-off-by: Radim Krčmář [james.hogan@imgtec.com: Backport to v4.7] Signed-off-by: James Hogan Signed-off-by: Greg Kroah-Hartman --- arch/mips/kvm/tlb.c | 45 ++++++++++++++++++++++++++------------------- 1 file changed, 26 insertions(+), 19 deletions(-) --- a/arch/mips/kvm/tlb.c +++ b/arch/mips/kvm/tlb.c @@ -373,25 +373,32 @@ int kvm_mips_handle_mapped_seg_tlb_fault unsigned long entryhi = 0, entrylo0 = 0, entrylo1 = 0; struct kvm *kvm = vcpu->kvm; kvm_pfn_t pfn0, pfn1; + long tlb_lo[2]; int ret; - if ((tlb->tlb_hi & VPN2_MASK) == 0) { - pfn0 = 0; - pfn1 = 0; - } else { - if (kvm_mips_map_page(kvm, mips3_tlbpfn_to_paddr(tlb->tlb_lo0) - >> PAGE_SHIFT) < 0) - return -1; - - if (kvm_mips_map_page(kvm, mips3_tlbpfn_to_paddr(tlb->tlb_lo1) - >> PAGE_SHIFT) < 0) - return -1; - - pfn0 = kvm->arch.guest_pmap[mips3_tlbpfn_to_paddr(tlb->tlb_lo0) - >> PAGE_SHIFT]; - pfn1 = kvm->arch.guest_pmap[mips3_tlbpfn_to_paddr(tlb->tlb_lo1) - >> PAGE_SHIFT]; - } + tlb_lo[0] = tlb->tlb_lo0; + tlb_lo[1] = tlb->tlb_lo1; + + /* + * The commpage address must not be mapped to anything else if the guest + * TLB contains entries nearby, or commpage accesses will break. + */ + if (!((tlb->tlb_hi ^ KVM_GUEST_COMMPAGE_ADDR) & + VPN2_MASK & (PAGE_MASK << 1))) + tlb_lo[(KVM_GUEST_COMMPAGE_ADDR >> PAGE_SHIFT) & 1] = 0; + + if (kvm_mips_map_page(kvm, mips3_tlbpfn_to_paddr(tlb_lo[0]) + >> PAGE_SHIFT) < 0) + return -1; + + if (kvm_mips_map_page(kvm, mips3_tlbpfn_to_paddr(tlb_lo[1]) + >> PAGE_SHIFT) < 0) + return -1; + + pfn0 = kvm->arch.guest_pmap[mips3_tlbpfn_to_paddr(tlb_lo[0]) + >> PAGE_SHIFT]; + pfn1 = kvm->arch.guest_pmap[mips3_tlbpfn_to_paddr(tlb_lo[1]) + >> PAGE_SHIFT]; if (hpa0) *hpa0 = pfn0 << PAGE_SHIFT; @@ -401,9 +408,9 @@ int kvm_mips_handle_mapped_seg_tlb_fault /* Get attributes from the Guest TLB */ entrylo0 = mips3_paddr_to_tlbpfn(pfn0 << PAGE_SHIFT) | (0x3 << 3) | - (tlb->tlb_lo0 & MIPS3_PG_D) | (tlb->tlb_lo0 & MIPS3_PG_V); + (tlb_lo[0] & MIPS3_PG_D) | (tlb_lo[0] & MIPS3_PG_V); entrylo1 = mips3_paddr_to_tlbpfn(pfn1 << PAGE_SHIFT) | (0x3 << 3) | - (tlb->tlb_lo1 & MIPS3_PG_D) | (tlb->tlb_lo1 & MIPS3_PG_V); + (tlb_lo[1] & MIPS3_PG_D) | (tlb_lo[1] & MIPS3_PG_V); kvm_debug("@ %#lx tlb_lo0: 0x%08lx tlb_lo1: 0x%08lx\n", vcpu->arch.pc, tlb->tlb_lo0, tlb->tlb_lo1);