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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,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 6E127C43603 for ; Wed, 11 Dec 2019 15:29:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 402FE2173E for ; Wed, 11 Dec 2019 15:29:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576078195; bh=IpzqZ8U2q1cIKIIYL06rQOFBJOT+/SNNiKO5NCgdzgY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=bvEnLMpoEGEFE5CW829nnKZwBMQOeBP3botJtu8AKzFXuvrMnsrWK7A1O8Brg3GDO /req/oFX8wgNBZRO/sM6QjzlHzg9gmzNx9Duc4qpYSNnx9tgnCsOjxQL7cd61+/N3w GNdm492HllbLETqEZsJBxaLAUQaHlEtNi7j2f0vI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387697AbfLKP3x (ORCPT ); Wed, 11 Dec 2019 10:29:53 -0500 Received: from mail.kernel.org ([198.145.29.99]:36596 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387925AbfLKP3g (ORCPT ); Wed, 11 Dec 2019 10:29:36 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 555142465B; Wed, 11 Dec 2019 15:29:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576078175; bh=IpzqZ8U2q1cIKIIYL06rQOFBJOT+/SNNiKO5NCgdzgY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0OQ8oQtfkok95UgRMhau9VaKNBP/bUd6S0W0nDNulOuBk0UScPC00KoHk3/bH/WBZ GqyGBftl3p/+vSuyq6Uhp4kgQqRPHA7k4wjb+dF24v0qBNjZkOOpEXdaje1+CH1oSB hWRkUG9wk0hn5FWx05w0LNJ1ygPf8XemjYdMqBfA= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Mike Rapoport , Andrea Arcangeli , Daniel Colascione , Jann Horn , Lokesh Gidra , Nick Kralevich , Nosh Minwalla , Pavel Emelyanov , Tim Murray , Aleksa Sarai , Andrew Morton , Linus Torvalds , Sasha Levin , linux-fsdevel@vger.kernel.org Subject: [PATCH AUTOSEL 4.14 58/58] userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK Date: Wed, 11 Dec 2019 10:28:31 -0500 Message-Id: <20191211152831.23507-58-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191211152831.23507-1-sashal@kernel.org> References: <20191211152831.23507-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mike Rapoport [ Upstream commit 3c1c24d91ffd536de0a64688a9df7f49e58fadbc ] A while ago Andy noticed (http://lkml.kernel.org/r/CALCETrWY+5ynDct7eU_nDUqx=okQvjm=Y5wJvA4ahBja=CQXGw@mail.gmail.com) that UFFD_FEATURE_EVENT_FORK used by an unprivileged user may have security implications. As the first step of the solution the following patch limits the availably of UFFD_FEATURE_EVENT_FORK only for those having CAP_SYS_PTRACE. The usage of CAP_SYS_PTRACE ensures compatibility with CRIU. Yet, if there are other users of non-cooperative userfaultfd that run without CAP_SYS_PTRACE, they would be broken :( Current implementation of UFFD_FEATURE_EVENT_FORK modifies the file descriptor table from the read() implementation of uffd, which may have security implications for unprivileged use of the userfaultfd. Limit availability of UFFD_FEATURE_EVENT_FORK only for callers that have CAP_SYS_PTRACE. Link: http://lkml.kernel.org/r/1572967777-8812-2-git-send-email-rppt@linux.ibm.com Signed-off-by: Mike Rapoport Reviewed-by: Andrea Arcangeli Cc: Daniel Colascione Cc: Jann Horn Cc: Lokesh Gidra Cc: Nick Kralevich Cc: Nosh Minwalla Cc: Pavel Emelyanov Cc: Tim Murray Cc: Aleksa Sarai Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- fs/userfaultfd.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index a609d480606da..e2b2196fd9428 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1807,13 +1807,12 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx, if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api))) goto out; features = uffdio_api.features; - if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES)) { - memset(&uffdio_api, 0, sizeof(uffdio_api)); - if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) - goto out; - ret = -EINVAL; - goto out; - } + ret = -EINVAL; + if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES)) + goto err_out; + ret = -EPERM; + if ((features & UFFD_FEATURE_EVENT_FORK) && !capable(CAP_SYS_PTRACE)) + goto err_out; /* report all available features and ioctls to userland */ uffdio_api.features = UFFD_API_FEATURES; uffdio_api.ioctls = UFFD_API_IOCTLS; @@ -1826,6 +1825,11 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx, ret = 0; out: return ret; +err_out: + memset(&uffdio_api, 0, sizeof(uffdio_api)); + if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) + ret = -EFAULT; + goto out; } static long userfaultfd_ioctl(struct file *file, unsigned cmd, -- 2.20.1