From patchwork Fri May 1 13:21:27 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 226474 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 6C710C47253 for ; Fri, 1 May 2020 14:00:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4BE05206D9 for ; Fri, 1 May 2020 14:00:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588341652; bh=vE4sw5pXGrs+jUPMxqzbdGisJdgJaBReRiGMoZcKJXw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=tLa/tD1ZbZ/1mXPKAq4P3D7pELsNkieOOZuDpA6rdyfUdwMD0cKwZJAVw1CeOp3r7 OORZyuFu1sqiiEB4rvrqqr1/AEgF9ecr3IQi6myDKtdHn912AFQO7dSIcTvOyjcK8I X4fAQPnyuJ8NgrwTrDrJEkmCrXw878UejC3mXJOA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729039AbgEAOAs (ORCPT ); Fri, 1 May 2020 10:00:48 -0400 Received: from mail.kernel.org ([198.145.29.99]:48964 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728933AbgEAN06 (ORCPT ); Fri, 1 May 2020 09:26:58 -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 DCE50208D6; Fri, 1 May 2020 13:26:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588339618; bh=vE4sw5pXGrs+jUPMxqzbdGisJdgJaBReRiGMoZcKJXw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nUoZaNG9/BX5DKHfbWdFjxbAvR7Czu3epjTfwmLLPrcs+CJBy6ZdSWCRCmcyRLJf1 NDs3tk7h2dWmLuyZ1seY+DxEPx2K/kMKLX4NvGPx25B4/qPkYhqL6akjtks1wl5Xc7 7GfKLlFC3yjPVx4Zt44r27ybpcFWKaO5Ovgv5p5w= 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 4.4 39/70] KVM: Check validity of resolved slot when searching memslots Date: Fri, 1 May 2020 15:21:27 +0200 Message-Id: <20200501131525.781677076@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200501131513.302599262@linuxfoundation.org> References: <20200501131513.302599262@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@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 @@ -934,7 +934,7 @@ 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];