From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Subject: [v2,1/2] ras: fix an off-by-one error in __find_elem() From: Borislav Petkov Message-Id: <20190416214634.GP31772@zn.tnic> Date: Tue, 16 Apr 2019 23:46:34 +0200 To: Cong Wang Cc: linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org, Tony Luck , Thomas Gleixner List-ID: T24gVHVlLCBBcHIgMTYsIDIwMTkgYXQgMDI6MzM6NTBQTSAtMDcwMCwgQ29uZyBXYW5nIHdyb3Rl Ogo+IGNlX2Fyci5hcnJheVtdIGlzIGFsd2F5cyB3aXRoaW4gdGhlIHJhbmdlIFswLCBjZV9hcnIu bi0xXS4KPiBIb3dldmVyLCB0aGUgYmluYXJ5IHNlYXJjaCBjb2RlIGluIF9fZmluZF9lbGVtKCkg dXNlcyBjZV9hcnIubgo+IGFzIHRoZSBtYXhpbXVtIGluZGV4LCB3aGljaCBjb3VsZCBsZWFkIHRv IGFuIG9mZi1ieS1vbmUKPiBvdXQtb2YtYm91bmQgYWNjZXNzIHJpZ2h0IGFmdGVyIHRoZSB3aGls ZSBsb29wLiBJbiB0aGlzIGNhc2UsCj4gd2Ugc2hvdWxkIG5vdCBldmVuIHJlYWQgaXQsIGp1c3Qg cmV0dXJuIC1FTk9LRVkgaW5zdGVhZC4KPiAKPiBOb3RlLCB0aGlzIGNvdWxkIGNhdXNlIGEga2Vy bmVsIGNyYXNoIGlmIGNlX2Fyci5uIGlzIGV4YWN0bHkKPiBNQVhfRUxFTVMuCgoiQ291bGQgY2F1 c2UiPwoKSSdtIHN0aWxsIHdhaXRpbmcgZm9yIGEgZGVtb25zdHJhdGlvbi4gWW91IGNhbiBidWls ZCBhIGNhc2UgdGhyb3VnaAp3cml0aW5nIHZhbHVlcyBpbiB0aGUgZGVidWdmcyBub2RlcyBJIHBv aW50ZWQgeW91IGF0IG9yIGV2ZW4gd2l0aCBhCnBhdGNoIG9udG9wIHByZXBhcmluZyB0aGUgZXhh Y3QgY29uZGl0aW9ucyBmb3IgaXQgdG8gY3Jhc2guIEFuZCB0aGVuCmdpdmUgbWUgdGhhdCAicmVj aXBlIiB0byB0cmlnZ2VyIGl0IGhlcmUgaW4gYSBWTS4KClRoeC4K 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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 E6294C10F13 for ; Tue, 16 Apr 2019 21:46:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AED1520868 for ; Tue, 16 Apr 2019 21:46:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="jCN9oOya" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727942AbfDPVqj (ORCPT ); Tue, 16 Apr 2019 17:46:39 -0400 Received: from mail.skyhub.de ([5.9.137.197]:41148 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727136AbfDPVqj (ORCPT ); Tue, 16 Apr 2019 17:46:39 -0400 Received: from zn.tnic (p200300EC2F0D69000C2D4197130645E8.dip0.t-ipconnect.de [IPv6:2003:ec:2f0d:6900:c2d:4197:1306:45e8]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id C85C51EC01B6; Tue, 16 Apr 2019 23:46:37 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1555451197; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=dpt/fldlEgPxBxaMDLtjZFykCgm8xUXXH6mMgn+tt0c=; b=jCN9oOyazxwTZuZaE+T3BjWqopQz9i83Fmm7U2X8itRE2FLKDFn1733kCye5DpVN1bnmJt LuE1MhocjgtIj6gtkpBiKwO8sIXYuWBpZRK5Q2dEHv1GOVau30yc4dCCvZ6RqSKtdHdix8 7wgmQaz4DjYDNmWMpWMfDD4jHNqHApQ= Date: Tue, 16 Apr 2019 23:46:34 +0200 From: Borislav Petkov To: Cong Wang Cc: linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org, Tony Luck , Thomas Gleixner Subject: Re: [PATCH v2 1/2] ras: fix an off-by-one error in __find_elem() Message-ID: <20190416214634.GP31772@zn.tnic> References: <20190416213351.28999-1-xiyou.wangcong@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline In-Reply-To: <20190416213351.28999-1-xiyou.wangcong@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-edac-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-edac@vger.kernel.org Message-ID: <20190416214634.4CnLLdyGfDXCZuGKfzuyuxsaSeA_Vafnh9cP4TaWxnw@z> On Tue, Apr 16, 2019 at 02:33:50PM -0700, Cong Wang wrote: > ce_arr.array[] is always within the range [0, ce_arr.n-1]. > However, the binary search code in __find_elem() uses ce_arr.n > as the maximum index, which could lead to an off-by-one > out-of-bound access right after the while loop. In this case, > we should not even read it, just return -ENOKEY instead. > > Note, this could cause a kernel crash if ce_arr.n is exactly > MAX_ELEMS. "Could cause"? I'm still waiting for a demonstration. You can build a case through writing values in the debugfs nodes I pointed you at or even with a patch ontop preparing the exact conditions for it to crash. And then give me that "recipe" to trigger it here in a VM. Thx. -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.