From patchwork Thu Jul 13 12:17:50 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Aleksa Sarai X-Patchwork-Id: 13312219 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A1721EB64DD for ; Thu, 13 Jul 2023 13:36:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233674AbjGMNgr (ORCPT ); Thu, 13 Jul 2023 09:36:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39878 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235076AbjGMNgo (ORCPT ); Thu, 13 Jul 2023 09:36:44 -0400 X-Greylist: delayed 2401 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Thu, 13 Jul 2023 06:36:37 PDT Received: from mout-p-103.mailbox.org (mout-p-103.mailbox.org [IPv6:2001:67c:2050:0:465::103]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1F81C2D40; Thu, 13 Jul 2023 06:36:36 -0700 (PDT) Received: from smtp1.mailbox.org (smtp1.mailbox.org [10.196.197.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-384) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-103.mailbox.org (Postfix) with ESMTPS id 4R1tvC4NGRz9sn9; Thu, 13 Jul 2023 14:19:03 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cyphar.com; s=MBO0001; t=1689250743; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=xpxD6jJvH2NdvxBxxbA/xwwWPK026oBkIsxvhSiVppQ=; b=J67hj0asCAtelzLhPQXRrS+E99al7I+BMNtQLJqGszQMeBH8Oi6tEK67X9nMQw4qlX7wnP +LA3S4+9ltR61EsvICm2rmjjJXhQ3MkQ89Ht0WK+0Y2DpXvYW0cThade6zZUIV/YXFgiJD 3X888cF2MvyASCky3OlN1BCR1QiJprtt/kc5/V+OD2qO2Dsbhq6GtGsv5sozeysXT4uFdv RexNELuNQXxbzZjT3OAHIVJrVyE0Z2GrrCDmMnlJ+EPOH+ntjEukAwcxeynzUATx00+/ec O1KjlREZGDtSYA82dFoqVAaaphuq3Hv/WOjIPJKcrjfKmzjiwIYCZKXlsDEZ+A== From: Aleksa Sarai To: Willy Tarreau , Shuah Khan , Christian Brauner , Andrew Morton , Dave Chinner , Al Viro , xu xin , Zhihao Cheng , Chao Yu , "Liam R. Howlett" , Janis Danisevskis , Kees Cook Cc: Aleksa Sarai , stable@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH] procfs: block chmod on /proc/thread-self/comm Date: Thu, 13 Jul 2023 22:17:50 +1000 Message-ID: <20230713121752.8039-1-cyphar@cyphar.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Due to an oversight in commit 1b3044e39a89 ("procfs: fix pthread cross-thread naming if !PR_DUMPABLE") in switching from REG to NOD, chmod operations on /proc/thread-self/comm were no longer blocked as they are on almost all other procfs files. A very similar situation with /proc/self/environ was used to as a root exploit a long time ago, but procfs has SB_I_NOEXEC so this is simply a correctness issue. Ref: https://lwn.net/Articles/191954/ Ref: 6d76fa58b050 ("Don't allow chmod() on the /proc// files") Fixes: 1b3044e39a89 ("procfs: fix pthread cross-thread naming if !PR_DUMPABLE") Cc: stable@vger.kernel.org # v4.7+ Signed-off-by: Aleksa Sarai --- fs/proc/base.c | 3 ++- tools/testing/selftests/nolibc/nolibc-test.c | 4 ++++ 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index 05452c3b9872..7394229816f3 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -3583,7 +3583,8 @@ static int proc_tid_comm_permission(struct mnt_idmap *idmap, } static const struct inode_operations proc_tid_comm_inode_operations = { - .permission = proc_tid_comm_permission, + .setattr = proc_setattr, + .permission = proc_tid_comm_permission, }; /* diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c index 486334981e60..08f0969208eb 100644 --- a/tools/testing/selftests/nolibc/nolibc-test.c +++ b/tools/testing/selftests/nolibc/nolibc-test.c @@ -580,6 +580,10 @@ int run_syscall(int min, int max) CASE_TEST(chmod_net); EXPECT_SYSZR(proc, chmod("/proc/self/net", 0555)); break; CASE_TEST(chmod_self); EXPECT_SYSER(proc, chmod("/proc/self", 0555), -1, EPERM); break; CASE_TEST(chown_self); EXPECT_SYSER(proc, chown("/proc/self", 0, 0), -1, EPERM); break; + CASE_TEST(chmod_self_comm); EXPECT_SYSER(proc, chmod("/proc/self/comm", 0777), -1, EPERM); break; + CASE_TEST(chmod_tid_comm); EXPECT_SYSER(proc, chmod("/proc/thread-self/comm", 0777), -1, EPERM); break; + CASE_TEST(chmod_self_environ);EXPECT_SYSER(proc, chmod("/proc/self/environ", 0777), -1, EPERM); break; + CASE_TEST(chmod_tid_environ); EXPECT_SYSER(proc, chmod("/proc/thread-self/environ", 0777), -1, EPERM); break; CASE_TEST(chroot_root); EXPECT_SYSZR(euid0, chroot("/")); break; CASE_TEST(chroot_blah); EXPECT_SYSER(1, chroot("/proc/self/blah"), -1, ENOENT); break; CASE_TEST(chroot_exe); EXPECT_SYSER(proc, chroot("/proc/self/exe"), -1, ENOTDIR); break;