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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02C60C47253 for ; Fri, 1 May 2020 13:29:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D71B7208C3 for ; Fri, 1 May 2020 13:29:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588339784; bh=74iTO465UoUa8Ze5YwNrtetiBHOrvZsrEsFg1HbTjFI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=EAxLWagIfjLqpz8bkyTboTHbWZRiTYvbwMr3GVKltAOO1NsMevtRiLtHBRIUvjeDJ 669poFNbqitpIL6i24ki8M2nfjD+jv3RstwI3EA5rnYqOD23aBe/ET+r05CSvBonL/ Pz6uQm43zj06HGPi3I9Dkekn6dqsxQ/YwBa91UiE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729318AbgEAN3n (ORCPT ); Fri, 1 May 2020 09:29:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:53242 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729302AbgEAN3i (ORCPT ); Fri, 1 May 2020 09:29:38 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CC928208DB; Fri, 1 May 2020 13:29:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588339778; bh=74iTO465UoUa8Ze5YwNrtetiBHOrvZsrEsFg1HbTjFI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=c/cxlIA/DwAnUActfiSs/idlbkRCmZ5ZmjewzcgcUTjtA9aVx9yWW2uTLtf7T38+a PIi7k3EvlJ+b0STtxVykCMvIM5ESZaMx792qe2KeTrVRTZ3NoIGVH38zvpkpOHi1Y1 Lgfh9Cg0dvUgyr2hiS4hi2NJeLAM8Jhk0kgCdfx8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+d889b59b2bb87d4047a2@syzkaller.appspotmail.com, Sean Christopherson , Cornelia Huck , Paolo Bonzini Subject: [PATCH 4.9 44/80] KVM: Check validity of resolved slot when searching memslots Date: Fri, 1 May 2020 15:21:38 +0200 Message-Id: <20200501131527.509549308@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200501131513.810761598@linuxfoundation.org> References: <20200501131513.810761598@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Sean Christopherson commit b6467ab142b708dd076f6186ca274f14af379c72 upstream. Check that the resolved slot (somewhat confusingly named 'start') is a valid/allocated slot before doing the final comparison to see if the specified gfn resides in the associated slot. The resolved slot can be invalid if the binary search loop terminated because the search index was incremented beyond the number of used slots. This bug has existed since the binary search algorithm was introduced, but went unnoticed because KVM statically allocated memory for the max number of slots, i.e. the access would only be truly out-of-bounds if all possible slots were allocated and the specified gfn was less than the base of the lowest memslot. Commit 36947254e5f98 ("KVM: Dynamically size memslot array based on number of used slots") eliminated the "all possible slots allocated" condition and made the bug embarrasingly easy to hit. Fixes: 9c1a5d38780e6 ("kvm: optimize GFN to memslot lookup with large slots amount") Reported-by: syzbot+d889b59b2bb87d4047a2@syzkaller.appspotmail.com Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson Message-Id: <20200408064059.8957-2-sean.j.christopherson@intel.com> Reviewed-by: Cornelia Huck Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- include/linux/kvm_host.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -914,7 +914,7 @@ search_memslots(struct kvm_memslots *slo start = slot + 1; } - if (gfn >= memslots[start].base_gfn && + if (start < slots->used_slots && gfn >= memslots[start].base_gfn && gfn < memslots[start].base_gfn + memslots[start].npages) { atomic_set(&slots->lru_slot, start); return &memslots[start];