From patchwork Thu May 5 19:39:39 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thadeu Lima de Souza Cascardo X-Patchwork-Id: 1627190 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: bilbo.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=canonical.com header.i=@canonical.com header.a=rsa-sha256 header.s=20210705 header.b=R2GYyZcx; dkim-atps=neutral Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=lists.ubuntu.com (client-ip=91.189.94.19; helo=huckleberry.canonical.com; envelope-from=kernel-team-bounces@lists.ubuntu.com; receiver=) Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by bilbo.ozlabs.org (Postfix) with ESMTPS id 4KvPFQ26fxz9sBF for ; Fri, 6 May 2022 05:40:56 +1000 (AEST) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.86_2) (envelope-from ) id 1nmhLB-0007VU-In; Thu, 05 May 2022 19:40:45 +0000 Received: from smtp-relay-canonical-1.internal ([10.131.114.174] helo=smtp-relay-canonical-1.canonical.com) by huckleberry.canonical.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1nmhL9-0007VM-Ew for kernel-team@lists.ubuntu.com; Thu, 05 May 2022 19:40:43 +0000 Received: from localhost.localdomain (1.general.cascardo.us.vpn [10.172.70.58]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by smtp-relay-canonical-1.canonical.com (Postfix) with ESMTPSA id 655513F653 for ; Thu, 5 May 2022 19:40:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=canonical.com; s=20210705; t=1651779643; bh=1r3fHV/GU3FCLpldGTUn9ooLz48Wz8ra8qilK3vRlFw=; h=From:To:Subject:Date:Message-Id:MIME-Version; b=R2GYyZcxYb5hV9y2Z8Vw4mRVvfEjAK1LfZr5fyAWJbdrXrp7o7pooJbYhW1tG5Uia aYMVU5FyRr/nyPc0NtaL1G1wjX5SG8tg6R59rW528bpE0r+2HiyGso8jUbSNVAvJWV 33P2ikFCQmkQ2+fbvn9PhgkhF7FuM79GJwKO1UhojFc53QAaehjf4aI6o1f2ehoyOL l0OVYW1SrigHlqI/JUpsmJ6mT7wEnMR19cDvIopgmf5oVd495r3ION2/ez099FwTAX joVTL7q7b9+C3uqParDMRUYtxThH1KSoaTtuZdfFqacocX38KJr90/vNDdno6nqt7G ZMxM5rvsCS3Jw== From: Thadeu Lima de Souza Cascardo To: kernel-team@lists.ubuntu.com Subject: [SRU Impish] KVM: x86/mmu: do compare-and-exchange of gPTE via the user address Date: Thu, 5 May 2022 16:39:39 -0300 Message-Id: <20220505193939.3754679-1-cascardo@canonical.com> X-Mailer: git-send-email 2.32.0 MIME-Version: 1.0 X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.20 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: "kernel-team" From: Paolo Bonzini commit 2a8859f373b0a86f0ece8ec8312607eacf12485d upstream. FNAME(cmpxchg_gpte) is an inefficient mess. It is at least decent if it can go through get_user_pages_fast(), but if it cannot then it tries to use memremap(); that is not just terribly slow, it is also wrong because it assumes that the VM_PFNMAP VMA is contiguous. The right way to do it would be to do the same thing as hva_to_pfn_remapped() does since commit add6a0cd1c5b ("KVM: MMU: try to fix up page faults before giving up", 2016-07-05), using follow_pte() and fixup_user_fault() to determine the correct address to use for memremap(). To do this, one could for example extract hva_to_pfn() for use outside virt/kvm/kvm_main.c. But really there is no reason to do that either, because there is already a perfectly valid address to do the cmpxchg() on, only it is a userspace address. That means doing user_access_begin()/user_access_end() and writing the code in assembly to handle exceptions correctly. Worse, the guest PTE can be 8-byte even on i686 so there is the extra complication of using cmpxchg8b to account for. But at least it is an efficient mess. (Thanks to Linus for suggesting improvement on the inline assembly). Reported-by: Qiuhao Li Reported-by: Gaoning Pan Reported-by: Yongkang Jia Reported-by: syzbot+6cde2282daa792c49ab8@syzkaller.appspotmail.com Debugged-by: Tadeusz Struk Tested-by: Maxim Levitsky Cc: stable@vger.kernel.org Fixes: bd53cb35a3e9 ("X86/KVM: Handle PFNs outside of kernel reach when touching GPTEs") Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman (cherry picked from commit 8771d9673e0bdb7148299f3c074667124bde6dff linux-5.15.y) CVE-2022-1158 Signed-off-by: Thadeu Lima de Souza Cascardo Acked-by: Luke Nowakowski-Krijger Acked-by: Stefan Bader --- arch/x86/kvm/mmu/paging_tmpl.h | 77 ++++++++++++++++------------------ 1 file changed, 37 insertions(+), 40 deletions(-) diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h index 45160fe80098..20a269bce359 100644 --- a/arch/x86/kvm/mmu/paging_tmpl.h +++ b/arch/x86/kvm/mmu/paging_tmpl.h @@ -34,9 +34,8 @@ #define PT_HAVE_ACCESSED_DIRTY(mmu) true #ifdef CONFIG_X86_64 #define PT_MAX_FULL_LEVELS PT64_ROOT_MAX_LEVEL - #define CMPXCHG cmpxchg + #define CMPXCHG "cmpxchgq" #else - #define CMPXCHG cmpxchg64 #define PT_MAX_FULL_LEVELS 2 #endif #elif PTTYPE == 32 @@ -52,7 +51,7 @@ #define PT_GUEST_DIRTY_SHIFT PT_DIRTY_SHIFT #define PT_GUEST_ACCESSED_SHIFT PT_ACCESSED_SHIFT #define PT_HAVE_ACCESSED_DIRTY(mmu) true - #define CMPXCHG cmpxchg + #define CMPXCHG "cmpxchgl" #elif PTTYPE == PTTYPE_EPT #define pt_element_t u64 #define guest_walker guest_walkerEPT @@ -65,7 +64,9 @@ #define PT_GUEST_DIRTY_SHIFT 9 #define PT_GUEST_ACCESSED_SHIFT 8 #define PT_HAVE_ACCESSED_DIRTY(mmu) ((mmu)->ept_ad) - #define CMPXCHG cmpxchg64 + #ifdef CONFIG_X86_64 + #define CMPXCHG "cmpxchgq" + #endif #define PT_MAX_FULL_LEVELS PT64_ROOT_MAX_LEVEL #else #error Invalid PTTYPE value @@ -147,43 +148,39 @@ static int FNAME(cmpxchg_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, pt_element_t __user *ptep_user, unsigned index, pt_element_t orig_pte, pt_element_t new_pte) { - int npages; - pt_element_t ret; - pt_element_t *table; - struct page *page; - - npages = get_user_pages_fast((unsigned long)ptep_user, 1, FOLL_WRITE, &page); - if (likely(npages == 1)) { - table = kmap_atomic(page); - ret = CMPXCHG(&table[index], orig_pte, new_pte); - kunmap_atomic(table); - - kvm_release_page_dirty(page); - } else { - struct vm_area_struct *vma; - unsigned long vaddr = (unsigned long)ptep_user & PAGE_MASK; - unsigned long pfn; - unsigned long paddr; - - mmap_read_lock(current->mm); - vma = find_vma_intersection(current->mm, vaddr, vaddr + PAGE_SIZE); - if (!vma || !(vma->vm_flags & VM_PFNMAP)) { - mmap_read_unlock(current->mm); - return -EFAULT; - } - pfn = ((vaddr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; - paddr = pfn << PAGE_SHIFT; - table = memremap(paddr, PAGE_SIZE, MEMREMAP_WB); - if (!table) { - mmap_read_unlock(current->mm); - return -EFAULT; - } - ret = CMPXCHG(&table[index], orig_pte, new_pte); - memunmap(table); - mmap_read_unlock(current->mm); - } + int r = -EFAULT; + + if (!user_access_begin(ptep_user, sizeof(pt_element_t))) + return -EFAULT; + +#ifdef CMPXCHG + asm volatile("1:" LOCK_PREFIX CMPXCHG " %[new], %[ptr]\n" + "mov $0, %[r]\n" + "setnz %b[r]\n" + "2:" + _ASM_EXTABLE_UA(1b, 2b) + : [ptr] "+m" (*ptep_user), + [old] "+a" (orig_pte), + [r] "+q" (r) + : [new] "r" (new_pte) + : "memory"); +#else + asm volatile("1:" LOCK_PREFIX "cmpxchg8b %[ptr]\n" + "movl $0, %[r]\n" + "jz 2f\n" + "incl %[r]\n" + "2:" + _ASM_EXTABLE_UA(1b, 2b) + : [ptr] "+m" (*ptep_user), + [old] "+A" (orig_pte), + [r] "+rm" (r) + : [new_lo] "b" ((u32)new_pte), + [new_hi] "c" ((u32)(new_pte >> 32)) + : "memory"); +#endif - return (ret != orig_pte); + user_access_end(); + return r; } static bool FNAME(prefetch_invalid_gpte)(struct kvm_vcpu *vcpu,