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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 69567C004D4 for ; Thu, 19 Jan 2023 18:02:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230012AbjASSCu (ORCPT ); Thu, 19 Jan 2023 13:02:50 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34566 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229914AbjASSCr (ORCPT ); Thu, 19 Jan 2023 13:02:47 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9AC6A9084C for ; Thu, 19 Jan 2023 10:02:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674151326; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=vaqYKA9gKcloEabUgO9UTR0QJlMjgtJTu1Mbgj1HV78=; b=SMhErcbea0DxHe/NuyZkcUTLkF7Akj8htj3g8ZMCWudPQKGHhDYiTZN+qwNrslkJ52P6Jx GXsoOgmYxPjFrHFM19OXk59coihd4LpuULYelqCq+NuzEoudoaUCG0NF7+MFRM8SgpSWxM tKPMf+/Hv0vK3zMPrG8XdeJzSAsdANQ= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-452-T3l97QkgOwK8iK2ynsYMNg-1; Thu, 19 Jan 2023 13:02:03 -0500 X-MC-Unique: T3l97QkgOwK8iK2ynsYMNg-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id DF7CA3803911; Thu, 19 Jan 2023 18:02:02 +0000 (UTC) Received: from localhost (unknown [10.39.195.23]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 78BDA492B02; Thu, 19 Jan 2023 18:02:02 +0000 (UTC) From: Giuseppe Scrivano To: Brian Masney Cc: linux-kernel@vger.kernel.org, keescook@chromium.org, bristot@redhat.com, ebiederm@xmission.com, brauner@kernel.org, cyphar@cyphar.com, viro@zeniv.linux.org.uk, alexl@redhat.com, peterz@infradead.org Subject: Re: [PATCH v2 1/2] exec: add PR_HIDE_SELF_EXE prctl References: <20230119170718.3129938-1-gscrivan@redhat.com> Date: Thu, 19 Jan 2023 19:02:00 +0100 In-Reply-To: (Brian Masney's message of "Thu, 19 Jan 2023 12:49:30 -0500") Message-ID: <87tu0mflnr.fsf@redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Brian Masney writes: > On Thu, Jan 19, 2023 at 06:07:17PM +0100, Giuseppe Scrivano wrote: >> This patch adds a new prctl called PR_HIDE_SELF_EXE which allows >> processes to hide their own /proc/*/exe file. When this prctl is >> used, every access to /proc/*/exe for the calling process will >> fail with ENOENT. >> >> This is useful for preventing issues like CVE-2019-5736, where an >> attacker can gain host root access by overwriting the binary >> in OCI runtimes through file-descriptor mishandling in containers. >> >> The current fix for CVE-2019-5736 is to create a read-only copy or >> a bind-mount of the current executable, and then re-exec the current >> process. With the new prctl, the read-only copy or bind-mount copy is >> not needed anymore. >> >> While map_files/ also might contain symlinks to files in host, >> proc_map_files_get_link() permissions checks are already sufficient. >> >> Signed-off-by: Giuseppe Scrivano >> --- >> fs/exec.c | 1 + >> fs/proc/base.c | 8 +++++--- >> include/linux/sched.h | 5 +++++ >> include/uapi/linux/prctl.h | 3 +++ >> kernel/sys.c | 9 +++++++++ >> tools/include/uapi/linux/prctl.h | 3 +++ >> 6 files changed, 26 insertions(+), 3 deletions(-) >> >> v1: https://lkml.org/lkml/2023/1/4/334 >> >> Differences from v1: >> >> - amended more information in the commit message wrt map_files not >> requiring the same protection. >> - changed the test to verify PR_HIDE_SELF_EXE cannot be unset after >> a fork. >> >> diff --git a/fs/exec.c b/fs/exec.c >> index ab913243a367..5a5dd964c3a3 100644 >> --- a/fs/exec.c >> +++ b/fs/exec.c >> @@ -1855,6 +1855,7 @@ static int bprm_execve(struct linux_binprm *bprm, >> /* execve succeeded */ >> current->fs->in_exec = 0; >> current->in_execve = 0; >> + task_clear_hide_self_exe(current); > > [snip] > >> rseq_execve(current); >> acct_update_integrals(current); >> task_numa_free(current, false); >> diff --git a/fs/proc/base.c b/fs/proc/base.c >> index 9e479d7d202b..959968e2da0d 100644 >> --- a/fs/proc/base.c >> +++ b/fs/proc/base.c >> @@ -1723,19 +1723,21 @@ static int proc_exe_link(struct dentry *dentry, struct path *exe_path) >> { >> struct task_struct *task; >> struct file *exe_file; >> + long hide_self_exe; >> >> task = get_proc_task(d_inode(dentry)); >> if (!task) >> return -ENOENT; >> exe_file = get_task_exe_file(task); >> + hide_self_exe = task_hide_self_exe(task); > > Perhaps I am missing something, but where is task_clear_hide_self_exe() > and task_hide_self_exe() defined? they are defined with: TASK_PFA_TEST(HIDE_SELF_EXE, hide_self_exe) TASK_PFA_SET(HIDE_SELF_EXE, hide_self_exe) TASK_PFA_CLEAR(HIDE_SELF_EXE, hide_self_exe) Regards, Giuseppe