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 9A3E0C433EF for ; Mon, 27 Jun 2022 18:10:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240128AbiF0SKq (ORCPT ); Mon, 27 Jun 2022 14:10:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36056 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240121AbiF0SKn (ORCPT ); Mon, 27 Jun 2022 14:10:43 -0400 Received: from mail-pj1-x102c.google.com (mail-pj1-x102c.google.com [IPv6:2607:f8b0:4864:20::102c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 329A5B7C1 for ; Mon, 27 Jun 2022 11:10:43 -0700 (PDT) Received: by mail-pj1-x102c.google.com with SMTP id n16-20020a17090ade9000b001ed15b37424so10173679pjv.3 for ; Mon, 27 Jun 2022 11:10:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=E/xc4vvQ8vo4eVo9CE15HRjgjonsTfeZsZT+f2UzoE0=; b=YmN5ASGNqa/ZRD16iaGFqtUU2QPk+y0jvo/pT6kvq6W9KhcWBvi7wmLCledcGsT6U2 O0gMjbuPWmxA4xxZqNPRDJafX4cGb2vsEQ1w9ap0NoUjVWn9CX5DEm2wtpVSFdDol94q dFJ97nlXk0/9lojXOOYVl/DflLo+T2bPlRwF4iwJRDunSSJcFInx1zUCBQ0TWT42aQtm pB7t7Fq8aeXJM8eqO9YjCTe/cYqK6IGiyHj8qRy4J0xjYv0sCRF8IhHddrH69RDA7a8D Rui+8bb7g6bBF05UDxMiWy7RPmD3sjnkcD8huwBHNKL7KEqpod1FJRLucsUmoQmost+o bq2A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=E/xc4vvQ8vo4eVo9CE15HRjgjonsTfeZsZT+f2UzoE0=; b=6mDZMGCtcp+AoN8l85p2NNVLLele9q/YDJVZhFdK1qDh453uUZC3CI+O77LTBtpGPI 7abEAw9+OuR8pXCwSqrMe0vK6Mo/V7gGQ1zTsB8kyFdQPmWju2Rz+wcuND5DBrRCqfYu rxGoV8nsZN/Eev7N73Eop3S8HqZGFbUkO/V0zKnxUiEZ0HP2GQOdUseVdbfSiM7GUakc PHUQyYW1JbRJaQ6tLKWkuH23z97iI6ZchyeC/3vnkmicb+bVTlUyRQxQSsmrqB8GEfXS yi0eNpAv5TAd4dAwhl5L49ygZgp0+ZNje+9ZrI0vHW0CPDDpQ4FeLE9xCo6aDdPVBbGx XvjQ== X-Gm-Message-State: AJIora9OkjYpO7YDW8+Fx7c9hbrDbYOVxTiWyTFGnx9HAgROhsuCzWNL u7KhG8MGGaXJs1JxddDXJQb5Pg== X-Google-Smtp-Source: AGRyM1vbabjlhOLCSp+Rpm/zQgX2cUDD2rbX4ZYw7XBv3FtZVs8GpFw1rj9KQ0DTf2ewyH9dkOOKdQ== X-Received: by 2002:a17:90b:3584:b0:1ee:fa46:3986 with SMTP id mm4-20020a17090b358400b001eefa463986mr559605pjb.227.1656353442636; Mon, 27 Jun 2022 11:10:42 -0700 (PDT) Received: from google.com (123.65.230.35.bc.googleusercontent.com. [35.230.65.123]) by smtp.gmail.com with ESMTPSA id k21-20020a6568d5000000b0040d5abae51esm7441815pgt.91.2022.06.27.11.10.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Jun 2022 11:10:42 -0700 (PDT) Date: Mon, 27 Jun 2022 18:10:37 +0000 From: Sean Christopherson To: Peter Gonda Cc: kvm@vger.kernel.org, Greg Thelen , Paolo Bonzini , Tom Lendacky , linux-kernel@vger.kernel.org Subject: Re: [PATCH] KVM: SEV: Clear the pages pointer in sev_unpin_memory Message-ID: References: <20220627161123.1386853-1-pgonda@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220627161123.1386853-1-pgonda@google.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, Jun 27, 2022, Peter Gonda wrote: > Clear to the @pages array pointer in sev_unpin_memory to avoid leaving a > dangling pointer to invalid memory. > > Signed-off-by: Peter Gonda > Cc: Greg Thelen > Cc: Paolo Bonzini > Cc: Sean Christopherson > Cc: Tom Lendacky > Cc: kvm@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > --- > arch/x86/kvm/svm/sev.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index 309bcdb2f929..485ad86c01c6 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -452,6 +452,7 @@ static void sev_unpin_memory(struct kvm *kvm, struct page **pages, > unpin_user_pages(pages, npages); > kvfree(pages); > sev->pages_locked -= npages; > + *pages = NULL; Would this have helped detect a real bug? I generally like cleaning up, but this leaves things in a somewhat inconsistent state, e.g. when unpinning a kvm_enc_region, pages will be NULL but npages will be non-zero. It's somewhat moot because the region is immediately freed in that case, but that begs the question of what real benefit this provides. sev_dbg_crypt() is the only flow where there's much danger of a use-after-free. > } > > static void sev_clflush_pages(struct page *pages[], unsigned long npages) > -- > 2.37.0.rc0.161.g10f37bed90-goog >