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From: "Mickaël Salaün" <mic@digikod.net>
To: linux-kernel@vger.kernel.org, James Morris <jmorris@namei.org>,
	"Serge E . Hallyn" <serge@hallyn.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Richard Weinberger <richard@nod.at>
Cc: "Mickaël Salaün" <mic@digikod.net>,
	"Andy Lutomirski" <luto@amacapital.net>,
	"Anton Ivanov" <anton.ivanov@cambridgegreys.com>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Casey Schaufler" <casey@schaufler-ca.com>,
	"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>,
	"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,
	"Mickaël Salaün" <mic@linux.microsoft.com>
Subject: [PATCH v21 06/12] fs,security: Add sb_delete hook
Date: Thu,  8 Oct 2020 17:30:57 +0200	[thread overview]
Message-ID: <20201008153103.1155388-7-mic@digikod.net> (raw)
In-Reply-To: <20201008153103.1155388-1-mic@digikod.net>

From: Mickaël Salaün <mic@linux.microsoft.com>

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.

Cc: Al 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>
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.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 2a8c74d99015..a512d4796409 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 29df5075b35d..81f21861651e 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);
-- 
2.28.0


  parent reply	other threads:[~2020-10-08 15:32 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-08 15:30 [PATCH v21 00/12] Landlock LSM Mickaël Salaün
2020-10-08 15:30 ` [PATCH v21 01/12] landlock: Add object management Mickaël Salaün
2020-10-08 15:30 ` [PATCH v21 02/12] landlock: Add ruleset and domain management Mickaël Salaün
2020-10-08 15:30 ` [PATCH v21 03/12] landlock: Set up the security framework and manage credentials Mickaël Salaün
2020-10-08 15:30 ` [PATCH v21 04/12] landlock: Add ptrace restrictions Mickaël Salaün
2020-10-08 15:30 ` [PATCH v21 05/12] LSM: Infrastructure management of the superblock Mickaël Salaün
2020-10-08 15:30 ` Mickaël Salaün [this message]
2020-10-08 15:30 ` [PATCH v21 07/12] landlock: Support filesystem access-control Mickaël Salaün
2020-10-14 18:07   ` James Morris
2020-10-14 18:52     ` Mickaël Salaün
2020-10-14 19:13       ` Mickaël Salaün
2020-10-14 20:46         ` James Morris
2020-10-08 15:30 ` [PATCH v21 08/12] landlock: Add syscall implementations Mickaël Salaün
2020-10-08 15:31 ` [PATCH v21 09/12] arch: Wire up Landlock syscalls Mickaël Salaün
2020-10-08 15:31 ` [PATCH v21 10/12] selftests/landlock: Add initial tests Mickaël Salaün
2020-10-08 15:31 ` [PATCH v21 11/12] samples/landlock: Add a sandbox manager example Mickaël Salaün
2020-10-08 15:31 ` [PATCH v21 12/12] landlock: Add user and kernel documentation Mickaël Salaün
2020-10-15 12:31   ` Mickaël Salaün

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