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From: "Mickaël Salaün" <mic@digikod.net>
To: linux-kernel@vger.kernel.org
Cc: "Mickaël Salaün" <mic@digikod.net>,
	"Al Viro" <viro@zeniv.linux.org.uk>,
	"Andy Lutomirski" <luto@amacapital.net>,
	"Anton Ivanov" <anton.ivanov@cambridgegreys.com>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Casey Schaufler" <casey@schaufler-ca.com>,
	"James Morris" <jmorris@namei.org>,
	"Jann Horn" <jannh@google.com>, "Jeff Dike" <jdike@addtoit.com>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Kees Cook" <keescook@chromium.org>,
	"Michael Kerrisk" <mtk.manpages@gmail.com>,
	"Mickaël Salaün" <mickael.salaun@ssi.gouv.fr>,
	"Richard Weinberger" <richard@nod.at>,
	"Serge E . Hallyn" <serge@hallyn.com>,
	"Shuah Khan" <shuah@kernel.org>,
	"Vincent Dagonneau" <vincent.dagonneau@ssi.gouv.fr>,
	kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org,
	linux-arch@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org,
	linux-security-module@vger.kernel.org, x86@kernel.org
Subject: [PATCH v19 06/12] fs,security: Add sb_delete hook
Date: Tue,  7 Jul 2020 20:09:49 +0200
Message-ID: <20200707180955.53024-7-mic@digikod.net> (raw)
In-Reply-To: <20200707180955.53024-1-mic@digikod.net>

The sb_delete security hook is called when shutting down a superblock,
which may be useful to release kernel objects tied to the superblock's
lifetime (e.g. inodes).

This new hook is needed by Landlock to release (ephemerally) tagged
struct inodes.  This comes from the unprivileged nature of Landlock
described in the next commit.

Signed-off-by: Mickaël Salaün <mic@digikod.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: James Morris <jmorris@namei.org>
Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Serge E. Hallyn <serge@hallyn.com>
---

Changes since v17:
* Initial patch to replace the direct call to landlock_release_inodes()
  (requested by James Morris).
  https://lore.kernel.org/lkml/alpine.LRH.2.21.2005150536440.7929@namei.org/
---
 fs/super.c                    | 1 +
 include/linux/lsm_hook_defs.h | 1 +
 include/linux/lsm_hooks.h     | 2 ++
 include/linux/security.h      | 4 ++++
 security/security.c           | 5 +++++
 5 files changed, 13 insertions(+)

diff --git a/fs/super.c b/fs/super.c
index 904459b35119..d5517e49ccdf 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -454,6 +454,7 @@ void generic_shutdown_super(struct super_block *sb)
 		evict_inodes(sb);
 		/* only nonzero refcount inodes can have marks */
 		fsnotify_sb_delete(sb);
+		security_sb_delete(sb);
 
 		if (sb->s_dio_done_wq) {
 			destroy_workqueue(sb->s_dio_done_wq);
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index af998f93d256..2b855d6a299e 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -59,6 +59,7 @@ LSM_HOOK(int, 0, fs_context_dup, struct fs_context *fc,
 LSM_HOOK(int, -ENOPARAM, fs_context_parse_param, struct fs_context *fc,
 	 struct fs_parameter *param)
 LSM_HOOK(int, 0, sb_alloc_security, struct super_block *sb)
+LSM_HOOK(void, LSM_RET_VOID, sb_delete, struct super_block *sb)
 LSM_HOOK(void, LSM_RET_VOID, sb_free_security, struct super_block *sb)
 LSM_HOOK(void, LSM_RET_VOID, sb_free_mnt_opts, void *mnt_opts)
 LSM_HOOK(int, 0, sb_eat_lsm_opts, char *orig, void **mnt_opts)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 80c629d8a2ad..499f19a70a19 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -108,6 +108,8 @@
  *	allocated.
  *	@sb contains the super_block structure to be modified.
  *	Return 0 if operation was successful.
+ * @sb_delete:
+ *	Release objects tied to a superblock (e.g. inodes).
  * @sb_free_security:
  *	Deallocate and clear the sb->s_security field.
  *	@sb contains the super_block structure to be modified.
diff --git a/include/linux/security.h b/include/linux/security.h
index 0a0a03b36a3b..28b0ee6c7239 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -286,6 +286,7 @@ void security_bprm_committed_creds(struct linux_binprm *bprm);
 int security_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc);
 int security_fs_context_parse_param(struct fs_context *fc, struct fs_parameter *param);
 int security_sb_alloc(struct super_block *sb);
+void security_sb_delete(struct super_block *sb);
 void security_sb_free(struct super_block *sb);
 void security_free_mnt_opts(void **mnt_opts);
 int security_sb_eat_lsm_opts(char *options, void **mnt_opts);
@@ -614,6 +615,9 @@ static inline int security_sb_alloc(struct super_block *sb)
 	return 0;
 }
 
+static inline void security_sb_delete(struct super_block *sb)
+{ }
+
 static inline void security_sb_free(struct super_block *sb)
 { }
 
diff --git a/security/security.c b/security/security.c
index d60aa835b670..9337b511306c 100644
--- a/security/security.c
+++ b/security/security.c
@@ -898,6 +898,11 @@ int security_sb_alloc(struct super_block *sb)
 	return rc;
 }
 
+void security_sb_delete(struct super_block *sb)
+{
+	call_void_hook(sb_delete, sb);
+}
+
 void security_sb_free(struct super_block *sb)
 {
 	call_void_hook(sb_free_security, sb);
-- 
2.27.0


  parent reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-07 18:09 [PATCH v19 00/12] Landlock LSM Mickaël Salaün
2020-07-07 18:09 ` [PATCH v19 01/12] landlock: Add object management Mickaël Salaün
2020-07-07 18:09 ` [PATCH v19 02/12] landlock: Add ruleset and domain management Mickaël Salaün
2020-07-07 18:09 ` [PATCH v19 03/12] landlock: Set up the security framework and manage credentials Mickaël Salaün
2020-07-07 18:09 ` [PATCH v19 04/12] landlock: Add ptrace restrictions Mickaël Salaün
2020-07-07 18:09 ` [PATCH v19 05/12] LSM: Infrastructure management of the superblock Mickaël Salaün
2020-07-07 18:09 ` Mickaël Salaün [this message]
2020-07-07 18:09 ` [PATCH v19 07/12] landlock: Support filesystem access-control Mickaël Salaün
2020-07-07 20:11   ` Randy Dunlap
2020-07-08  7:03     ` Mickaël Salaün
2020-07-07 18:09 ` [PATCH v19 08/12] landlock: Add syscall implementation Mickaël Salaün
2020-07-08  8:57   ` Arnd Bergmann
2020-07-08 13:04     ` Mickaël Salaün
2020-07-08 13:49       ` Arnd Bergmann
2020-07-08 17:50         ` Mickaël Salaün
2020-07-09 17:26           ` Arnd Bergmann
2020-07-09 17:47             ` Christian Brauner
2020-07-10 12:57               ` Mickaël Salaün
2020-07-07 18:09 ` [PATCH v19 09/12] arch: Wire up landlock() syscall Mickaël Salaün
2020-07-08  7:22   ` Arnd Bergmann
2020-07-08  7:31     ` Mickaël Salaün
2020-07-08  7:47       ` Arnd Bergmann
2020-07-08  8:23         ` Mickaël Salaün
2020-07-08  8:58           ` Arnd Bergmann
2020-07-07 18:09 ` [PATCH v19 10/12] selftests/landlock: Add initial tests Mickaël Salaün
2020-07-07 18:09 ` [PATCH v19 11/12] samples/landlock: Add a sandbox manager example Mickaël Salaün
2020-07-07 18:09 ` [PATCH v19 12/12] landlock: Add user and kernel documentation Mickaël Salaün

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