From patchwork Thu Jul 13 12:19:04 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Aleksa Sarai X-Patchwork-Id: 13311939 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 02FACEB64DD for ; Thu, 13 Jul 2023 12:19:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234623AbjGMMT3 (ORCPT ); Thu, 13 Jul 2023 08:19:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42586 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234660AbjGMMT1 (ORCPT ); Thu, 13 Jul 2023 08:19:27 -0400 Received: from mout-p-102.mailbox.org (mout-p-102.mailbox.org [80.241.56.152]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5D02E2691; Thu, 13 Jul 2023 05:19:25 -0700 (PDT) Received: from smtp202.mailbox.org (smtp202.mailbox.org [IPv6:2001:67c:2050:b231:465::202]) (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-102.mailbox.org (Postfix) with ESMTPS id 4R1tvY219Sz9scb; Thu, 13 Jul 2023 14:19:21 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cyphar.com; s=MBO0001; t=1689250761; 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=cylZYD1v3/ux3bOiBo3SI+1bkuoVoVNqjUBtUccqLVf/rjbGuRgjZ0Z6usXEm/u3ktL1v8 71xqGF6BjvRUpF2MnI9/7rMzhIJe/qPc8YUXWpj0UYEfTX9ESVdtOBLWqZLgY7p++dgdWJ u3LO9hPOjKSXDO1Hdr9TLWSe9AaFE1cVOGBWKLQOC3KS9lCI8780JZMgKP2RRkDvY6wB8k O/ESIRtcVJZPbUKsdZQMUgeQ8k77eFHC/zczIBMUoA+jhMfQO7oJ+Ey0zEVYj5s+ez7voJ 3U9095AoedknarhqdaeQj74FN+bFWJ21aH9h5d0W5dmoY/1l3hvYwrOffueUmA== From: Aleksa Sarai To: Willy Tarreau , Shuah Khan , Andrew Morton , Christian Brauner , Dave Chinner , xu xin , Al Viro , Stefan Roesch , Aleksa Sarai , Zhihao Cheng , "Liam R. Howlett" , Janis Danisevskis , Kees Cook Cc: 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 22:19:04 +1000 Message-ID: <20230713121907.9693-1-cyphar@cyphar.com> MIME-Version: 1.0 X-Rspamd-Queue-Id: 4R1tvY219Sz9scb 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;