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 61C8EC433FE for ; Tue, 18 Oct 2022 15:02:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230346AbiJRPCZ (ORCPT ); Tue, 18 Oct 2022 11:02:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39574 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230288AbiJRPCY (ORCPT ); Tue, 18 Oct 2022 11:02:24 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6E4A6DBBFC; Tue, 18 Oct 2022 08:02:23 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id C80A0B81F94; Tue, 18 Oct 2022 15:02:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 83774C433D6; Tue, 18 Oct 2022 15:02:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1666105340; bh=7/gSW/YAwojZ7rDGfHVc1ctabTFOpK3OWU/NQqBOtHw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Z5kp4mGnLs85wnBjb8szwJHbw6vmzj0gjEP0Ax2jCOP4VnQBuRMnYScTtWnrLL7m1 95xDI/uLa/XJRtnpCd8qysURAtjDI8sLjrcBrpZYkoYdg3MLHqoJ0ttyA/TQaAVGnX /hvlUH1S9Ctx3z3lg0pTDBIRUsQ3fg9xXEHwqZt0cSMTSlkiT1Z5YztBWjgEKCbs/C GIinoNw8dk+WoyOACVLfZtKNZCx8Erx9fl8zJPLQnj134LcIPJ/i3GK450IE8AWQk2 sZzldoCpKcURVr/9R1xLQlrplM6nTh3LEurTV+9UplsOPwq22QgPp/2KwprRdS/8Pe MdcZDlbKEhjKQ== Date: Tue, 18 Oct 2022 17:02:13 +0200 From: Christian Brauner To: Kees Cook Cc: Mimi Zohar , Dmitry Kasatkin , Paul Moore , James Morris , "Serge E. Hallyn" , Petr Vorel , Jonathan McDowell , Borislav Petkov , Takashi Iwai , linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, =?utf-8?Q?Micka=C3=ABl_Sala=C3=BCn?= , KP Singh , Casey Schaufler , John Johansen , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH 4/9] ima: Move ima_file_free() into LSM Message-ID: <20221018150213.7n4sv7rtsh6lshd5@wittgenstein> References: <20221013222702.never.990-kees@kernel.org> <20221013223654.659758-4-keescook@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20221013223654.659758-4-keescook@chromium.org> Precedence: bulk List-ID: On Thu, Oct 13, 2022 at 03:36:49PM -0700, Kees Cook wrote: > The file_free_security hook already exists for managing notification of > released files. Use the LSM hook instead of open-coded stacking. > > Cc: Mimi Zohar > Cc: Dmitry Kasatkin > Cc: Paul Moore > Cc: James Morris > Cc: "Serge E. Hallyn" > Cc: Petr Vorel > Cc: Jonathan McDowell > Cc: Borislav Petkov > Cc: Takashi Iwai > Cc: linux-integrity@vger.kernel.org > Cc: linux-security-module@vger.kernel.org > Signed-off-by: Kees Cook > --- > fs/file_table.c | 1 - > include/linux/ima.h | 6 ------ > security/integrity/ima/ima_main.c | 3 ++- > 3 files changed, 2 insertions(+), 8 deletions(-) > > diff --git a/fs/file_table.c b/fs/file_table.c > index 99c6796c9f28..fa707d221a43 100644 > --- a/fs/file_table.c > +++ b/fs/file_table.c > @@ -311,7 +311,6 @@ static void __fput(struct file *file) > eventpoll_release(file); > locks_remove_file(file); > > - ima_file_free(file); > if (unlikely(file->f_flags & FASYNC)) { > if (file->f_op->fasync) > file->f_op->fasync(-1, file, 0); > diff --git a/include/linux/ima.h b/include/linux/ima.h > index 6dc5143f89f2..9f18df366064 100644 > --- a/include/linux/ima.h > +++ b/include/linux/ima.h > @@ -19,7 +19,6 @@ extern enum hash_algo ima_get_current_hash_algo(void); > extern int ima_file_check(struct file *file, int mask); > extern void ima_post_create_tmpfile(struct user_namespace *mnt_userns, > struct inode *inode); > -extern void ima_file_free(struct file *file); > extern void ima_post_path_mknod(struct user_namespace *mnt_userns, > struct dentry *dentry); > extern int ima_file_hash(struct file *file, char *buf, size_t buf_size); > @@ -56,11 +55,6 @@ static inline void ima_post_create_tmpfile(struct user_namespace *mnt_userns, > { > } > > -static inline void ima_file_free(struct file *file) > -{ > - return; > -} > - > static inline void ima_post_path_mknod(struct user_namespace *mnt_userns, > struct dentry *dentry) > { > diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c > index b3b79d030a67..94379ba40b58 100644 > --- a/security/integrity/ima/ima_main.c > +++ b/security/integrity/ima/ima_main.c > @@ -183,7 +183,7 @@ static void ima_check_last_writer(struct integrity_iint_cache *iint, > * > * Flag files that changed, based on i_version > */ > -void ima_file_free(struct file *file) > +static void ima_file_free(struct file *file) > { > struct inode *inode = file_inode(file); > struct integrity_iint_cache *iint; > @@ -1085,6 +1085,7 @@ static struct security_hook_list ima_hooks[] __lsm_ro_after_init = { > LSM_HOOK_INIT(bprm_check_security, ima_bprm_check), > LSM_HOOK_INIT(mmap_file, ima_file_mmap), > LSM_HOOK_INIT(file_mprotect, ima_file_mprotect), > + LSM_HOOK_INIT(file_free_security, ima_file_free), This doesn't work afaict. If the file is opened for writing ima may update xattrs. But by the time security_file_free() is called put_file_access() has already been called which will have given up write access to the file's mount. So you would have to - just one of the possibilities - have to move security_file_free() out of file_free() and into the old ima_file_free() location. But that might cause semantic changes for other LSMs.