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=-1.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 DFDF0C49ED6 for ; Wed, 11 Sep 2019 13:48:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B2D2520863 for ; Wed, 11 Sep 2019 13:48:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568209738; bh=2ZAB+MxpAQ5hJTPfjiPVljlb21WGGQdhzccadL1cdPs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=t6pCRsweYzfLdKTer0+dQxN2ZDS/jdynWQHB601NxZAac8Fd/X3IN756myW+RZmfp sZTR+FSKtImHCq2njX4v3iBxjCteB+h+6dUjMuC5Qd9apyLE8/IqJv+rX2wyKJtvDX 7MVMhHalMMVY0+9dzlbroZ5objvYI1Q6Vtsu1By0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728192AbfIKNs6 (ORCPT ); Wed, 11 Sep 2019 09:48:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:40804 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727093AbfIKNs5 (ORCPT ); Wed, 11 Sep 2019 09:48:57 -0400 Received: from X1 (110.8.30.213.rev.vodafone.pt [213.30.8.110]) (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 13A6A206CD; Wed, 11 Sep 2019 13:48:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568209737; bh=2ZAB+MxpAQ5hJTPfjiPVljlb21WGGQdhzccadL1cdPs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=yLZdyRICT5fdlJII7PdUmXMGmuN7rE8UOq/X4b1M1Mpki/JS7/vsvXA8KvGSmfXRb jdUZ+fJGg7XWaumbFjMoLNPNSgI6vV8coA/RvRaB4MIVKWhLbSSnuJXg/hxy99xE1y 9NYp9yLP20fZWnh+XuV1Bb7QYStdGeHy0gcvEPf4= Date: Wed, 11 Sep 2019 06:48:52 -0700 From: Andrew Morton To: Eugene Syromiatnikov Cc: linux-kernel@vger.kernel.org, Christian Brauner , Oleg Nesterov , "Peter Zijlstra (Intel)" , Ingo Molnar , "Dmitry V. Levin" , Eric Biederman Subject: Re: [PATCH v2] fork: check exit_signal passed in clone3() call Message-Id: <20190911064852.9f236d4c201b50e14d717c14@linux-foundation.org> In-Reply-To: <20190910175852.GA15572@asgard.redhat.com> References: <20190910175852.GA15572@asgard.redhat.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 10 Sep 2019 18:58:52 +0100 Eugene Syromiatnikov wrote: > Previously, higher 32 bits of exit_signal fields were lost when > copied to the kernel args structure (that uses int as a type for the > respective field). Moreover, as Oleg has noted[1], exit_signal is used > unchecked, so it has to be checked for sanity before use; for the legacy > syscalls, applying CSIGNAL mask guarantees that it is at least non-negative; > however, there's no such thing is done in clone3() code path, and that can > break at least thread_group_leader. > > Checking user-passed exit_signal against ~CSIGNAL mask solves both > of these problems. > > [1] https://lkml.org/lkml/2019/9/10/467 > > * kernel/fork.c (copy_clone_args_from_user): Fail with -EINVAL if > args.exit_signal has bits set outside CSIGNAL mask. > (_do_fork): Note that exit_signal is expected to be checked for the > sanity by the caller. > > Fixes: 7f192e3cd316 ("fork: add clone3") What are the user-visible runtime effects of this bug? Relatedly, should this fix be backported into -stable kernels? If so, why?