From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D44ABC433EF for ; Mon, 24 Jan 2022 19:17:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345856AbiAXTRT (ORCPT ); Mon, 24 Jan 2022 14:17:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47502 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345122AbiAXTJL (ORCPT ); Mon, 24 Jan 2022 14:09:11 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2E948C08C5C5; Mon, 24 Jan 2022 11:02:09 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id DF5E8B8119D; Mon, 24 Jan 2022 19:02:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1933BC340E5; Mon, 24 Jan 2022 19:02:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1643050926; bh=aDFoXBfXTkfoNdAUutnNPz0dvkoSMcKTMdxDWksInsE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Q6e4S11eXMhSJCVmeaL4dOJIAAQf+7vvXJQZ4/EQCXTxvCZVTM9LWWZyHh0fENWqD /CXwRqw2rrTGfxCFsO/aV91cA6q7xz23a1pW6TJmduy7b/4ZJAJ+DfCslK4bO8QR47 5RZzFxA4QCkBiy1VDDs3foHhsI/AHC6g/8GPnoTw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , Nicholas Piggin , Paolo Bonzini , Ben Hutchings Subject: [PATCH 4.9 157/157] KVM: do not allow mapping valid but non-reference-counted pages Date: Mon, 24 Jan 2022 19:44:07 +0100 Message-Id: <20220124183937.735989252@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220124183932.787526760@linuxfoundation.org> References: <20220124183932.787526760@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Nicholas Piggin commit f8be156be163a052a067306417cd0ff679068c97 upstream. It's possible to create a region which maps valid but non-refcounted pages (e.g., tail pages of non-compound higher order allocations). These host pages can then be returned by gfn_to_page, gfn_to_pfn, etc., family of APIs, which take a reference to the page, which takes it from 0 to 1. When the reference is dropped, this will free the page incorrectly. Fix this by only taking a reference on valid pages if it was non-zero, which indicates it is participating in normal refcounting (and can be released with put_page). This addresses CVE-2021-22543. Signed-off-by: Nicholas Piggin Tested-by: Paolo Bonzini Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman --- virt/kvm/kvm_main.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1513,6 +1513,13 @@ static bool vma_is_valid(struct vm_area_ return true; } +static int kvm_try_get_pfn(kvm_pfn_t pfn) +{ + if (kvm_is_reserved_pfn(pfn)) + return 1; + return get_page_unless_zero(pfn_to_page(pfn)); +} + static int hva_to_pfn_remapped(struct vm_area_struct *vma, unsigned long addr, bool *async, bool write_fault, bool *writable, @@ -1562,13 +1569,21 @@ static int hva_to_pfn_remapped(struct vm * Whoever called remap_pfn_range is also going to call e.g. * unmap_mapping_range before the underlying pages are freed, * causing a call to our MMU notifier. + * + * Certain IO or PFNMAP mappings can be backed with valid + * struct pages, but be allocated without refcounting e.g., + * tail pages of non-compound higher order allocations, which + * would then underflow the refcount when the caller does the + * required put_page. Don't allow those pages here. */ - kvm_get_pfn(pfn); + if (!kvm_try_get_pfn(pfn)) + r = -EFAULT; out: pte_unmap_unlock(ptep, ptl); *p_pfn = pfn; - return 0; + + return r; } /*