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 631E4C55189 for ; Wed, 22 Apr 2020 10:00:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3E9F02082E for ; Wed, 22 Apr 2020 10:00:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587549627; bh=wRvSAt//1Dl7jXusj8IViGumHNtyt3coDpWgMy+UbOI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=sStN9DX4vEmf/E0pPH5c4NVaiKDV1KHUzptl7pNswFzF7etSMXKpViarv+vjNKP4z 2o1bLXt8NMLasmKeukVz3kvidMV0i8mX83oGgbY60a7SkK7GL5OE/ptCzAHjS95TC5 6duXETfmfPim+YL9BdTTr+22Vkx08E3ujx3wm1Lo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726629AbgDVKAY (ORCPT ); Wed, 22 Apr 2020 06:00:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:47352 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726487AbgDVKAP (ORCPT ); Wed, 22 Apr 2020 06:00:15 -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 D7BD62077D; Wed, 22 Apr 2020 10:00:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587549614; bh=wRvSAt//1Dl7jXusj8IViGumHNtyt3coDpWgMy+UbOI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gxwCDm2Va/bC/GJ2GTXgvBX3vcdC2gCakg1uS+rPk8qy/8LD4QFQamVZ0RPReDJ5N FfJA2VTB/SlurIFbrZ35hDw+Jl0Yd+TWAMj8XaSPdz1tSLqyhl1hWQ1RbIbPMAI22/ +Wl/33VQVUeX1urYB59SVqvg/eR8XSr20ZLL28UE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jiri Slaby , Ingo Molnar , Peter Zijlstra , Darren Hart , Linus Torvalds , Guenter Roeck Subject: [PATCH 4.4 035/100] futex: futex_wake_op, do not fail on invalid op Date: Wed, 22 Apr 2020 11:56:05 +0200 Message-Id: <20200422095028.981138893@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200422095022.476101261@linuxfoundation.org> References: <20200422095022.476101261@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: Jiri Slaby commit e78c38f6bdd900b2ad9ac9df8eff58b745dc5b3c upstream. In commit 30d6e0a4190d ("futex: Remove duplicated code and fix undefined behaviour"), I let FUTEX_WAKE_OP to fail on invalid op. Namely when op should be considered as shift and the shift is out of range (< 0 or > 31). But strace's test suite does this madness: futex(0x7fabd78bcffc, 0x5, 0xfacefeed, 0xb, 0x7fabd78bcffc, 0xa0caffee); futex(0x7fabd78bcffc, 0x5, 0xfacefeed, 0xb, 0x7fabd78bcffc, 0xbadfaced); futex(0x7fabd78bcffc, 0x5, 0xfacefeed, 0xb, 0x7fabd78bcffc, 0xffffffff); When I pick the first 0xa0caffee, it decodes as: 0x80000000 & 0xa0caffee: oparg is shift 0x70000000 & 0xa0caffee: op is FUTEX_OP_OR 0x0f000000 & 0xa0caffee: cmp is FUTEX_OP_CMP_EQ 0x00fff000 & 0xa0caffee: oparg is sign-extended 0xcaf = -849 0x00000fff & 0xa0caffee: cmparg is sign-extended 0xfee = -18 That means the op tries to do this: (futex |= (1 << (-849))) == -18 which is completely bogus. The new check of op in the code is: if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28)) { if (oparg < 0 || oparg > 31) return -EINVAL; oparg = 1 << oparg; } which results obviously in the "Invalid argument" errno: FAIL: futex =========== futex(0x7fabd78bcffc, 0x5, 0xfacefeed, 0xb, 0x7fabd78bcffc, 0xa0caffee) = -1: Invalid argument futex.test: failed test: ../futex failed with code 1 So let us soften the failure to print only a (ratelimited) message, crop the value and continue as if it were right. When userspace keeps up, we can switch this to return -EINVAL again. [v2] Do not return 0 immediatelly, proceed with the cropped value. Fixes: 30d6e0a4190d ("futex: Remove duplicated code and fix undefined behaviour") Signed-off-by: Jiri Slaby Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Darren Hart Signed-off-by: Linus Torvalds Cc: Guenter Roeck Signed-off-by: Greg Kroah-Hartman --- kernel/futex.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1479,8 +1479,16 @@ static int futex_atomic_op_inuser(unsign int oldval, ret; if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28)) { - if (oparg < 0 || oparg > 31) - return -EINVAL; + if (oparg < 0 || oparg > 31) { + char comm[sizeof(current->comm)]; + /* + * kill this print and return -EINVAL when userspace + * is sane again + */ + pr_info_ratelimited("futex_wake_op: %s tries to shift op by %d; fix this program\n", + get_task_comm(comm, current), oparg); + oparg &= 31; + } oparg = 1 << oparg; }