From patchwork Mon Mar 15 14:22:34 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 401121 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=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_RED, USER_AGENT_GIT autolearn=ham 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 38DAAC4646C for ; Mon, 15 Mar 2021 14:25:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 218E7650AA for ; Mon, 15 Mar 2021 14:25:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232936AbhCOOYQ (ORCPT ); Mon, 15 Mar 2021 10:24:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:45602 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238316AbhCOOXE (ORCPT ); Mon, 15 Mar 2021 10:23:04 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 34A9764F5B; Mon, 15 Mar 2021 14:23:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1615818183; bh=iZVcEZOcdEE4W9T16bNkhWZ2XkC5r1kP4JwfYC3n7U0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MaR50pjzNy0n7f8yimemPXeaUG1OHFWUBDZR1c4IuonbnHJQ0Ssizy4xMY34UanLT Zz3wLQmaTpJ/zv7KRYvvORCkU20SfC9oAA4SwR1RNzpjWiPEf/OnldPUTi7odG6dPX pTJUK2hKfMXEaF1mlzkbm739lVWi16fD19hbH/gw= From: gregkh@linuxfoundation.org To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Suren Baghdasaryan , Kees Cook , Minchan Kim , David Rientjes , Jann Horn , Jeff Vander Stoep , Michal Hocko , Shakeel Butt , Tim Murray , Florian Weimer , Oleg Nesterov , James Morris , Andrew Morton , Linus Torvalds Subject: [PATCH 5.10 284/290] mm/madvise: replace ptrace attach requirement for process_madvise Date: Mon, 15 Mar 2021 15:22:34 +0100 Message-Id: <20210315135551.625694847@linuxfoundation.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210315135551.391322899@linuxfoundation.org> References: <20210315135541.921894249@linuxfoundation.org> <20210315135551.391322899@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Greg Kroah-Hartman From: Suren Baghdasaryan commit 96cfe2c0fd23ea7c2368d14f769d287e7ae1082e upstream. process_madvise currently requires ptrace attach capability. PTRACE_MODE_ATTACH gives one process complete control over another process. It effectively removes the security boundary between the two processes (in one direction). Granting ptrace attach capability even to a system process is considered dangerous since it creates an attack surface. This severely limits the usage of this API. The operations process_madvise can perform do not affect the correctness of the operation of the target process; they only affect where the data is physically located (and therefore, how fast it can be accessed). What we want is the ability for one process to influence another process in order to optimize performance across the entire system while leaving the security boundary intact. Replace PTRACE_MODE_ATTACH with a combination of PTRACE_MODE_READ and CAP_SYS_NICE. PTRACE_MODE_READ to prevent leaking ASLR metadata and CAP_SYS_NICE for influencing process performance. Link: https://lkml.kernel.org/r/20210303185807.2160264-1-surenb@google.com Signed-off-by: Suren Baghdasaryan Reviewed-by: Kees Cook Acked-by: Minchan Kim Acked-by: David Rientjes Cc: Jann Horn Cc: Jeff Vander Stoep Cc: Michal Hocko Cc: Shakeel Butt Cc: Tim Murray Cc: Florian Weimer Cc: Oleg Nesterov Cc: James Morris Cc: [5.10+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/madvise.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1202,12 +1202,22 @@ SYSCALL_DEFINE5(process_madvise, int, pi goto release_task; } - mm = mm_access(task, PTRACE_MODE_ATTACH_FSCREDS); + /* Require PTRACE_MODE_READ to avoid leaking ASLR metadata. */ + mm = mm_access(task, PTRACE_MODE_READ_FSCREDS); if (IS_ERR_OR_NULL(mm)) { ret = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH; goto release_task; } + /* + * Require CAP_SYS_NICE for influencing process performance. Note that + * only non-destructive hints are currently supported. + */ + if (!capable(CAP_SYS_NICE)) { + ret = -EPERM; + goto release_mm; + } + total_len = iov_iter_count(&iter); while (iov_iter_count(&iter)) { @@ -1222,6 +1232,7 @@ SYSCALL_DEFINE5(process_madvise, int, pi if (ret == 0) ret = total_len - iov_iter_count(&iter); +release_mm: mmput(mm); release_task: put_task_struct(task);