[PATCH 01/17] watch_queue: Add security hooks to rule on setting mount and sb watches [ver #17]

David Howells
2020-02-21T18:02:03Z

Add security hooks that will allow an LSM to rule on whether or not a watch
may be set on a mount or on a superblock. More than one hook is required
as the watches watch different types of object.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Casey Schaufler <casey@schaufler-ca.com>
cc: Stephen Smalley <sds@tycho.nsa.gov>
cc: linux-security-module@vger.kernel.org
---

include/linux/lsm_hooks.h | 24 ++++++++++++++++++++++++
include/linux/security.h | 16 ++++++++++++++++
security/security.c | 14 ++++++++++++++
3 files changed, 54 insertions(+)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 16530255dc11..c4451ac197ae 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1427,6 +1427,18 @@
* Check to see if a process is allowed to watch for event notifications
* from devices (as a global set).
*
+ * @watch_mount:
+ * Check to see if a process is allowed to watch for mount topology change
+ * notifications on a mount subtree.
+ * @watch: The watch object
+ * @path: The root of the subtree to watch.
+ *
+ * @watch_sb:
+ * Check to see if a process is allowed to watch for event notifications
+ * from a superblock.
+ * @watch: The watch object
+ * @sb: The superblock to watch.
+ *
* @post_notification:
* Check to see if a watch notification can be posted to a particular
* queue.
@@ -1722,6 +1734,12 @@ union security_list_options {
#ifdef CONFIG_DEVICE_NOTIFICATIONS
int (*watch_devices)(void);
#endif
+#ifdef CONFIG_MOUNT_NOTIFICATIONS
+ int (*watch_mount)(struct watch *watch, struct path *path);
+#endif
+#ifdef CONFIG_SB_NOTIFICATIONS
+ int (*watch_sb)(struct watch *watch, struct super_block *sb);
+#endif
#ifdef CONFIG_WATCH_QUEUE
int (*post_notification)(const struct cred *w_cred,
const struct cred *cred,
@@ -2020,6 +2038,12 @@ struct security_hook_heads {
#ifdef CONFIG_DEVICE_NOTIFICATIONS
struct hlist_head watch_devices;
#endif
+#ifdef CONFIG_MOUNT_NOTIFICATIONS
+ struct hlist_head watch_mount;
+#endif
+#ifdef CONFIG_SB_NOTIFICATIONS
+ struct hlist_head watch_sb;
+#endif
#ifdef CONFIG_WATCH_QUEUE
struct hlist_head post_notification;
#endif /* CONFIG_WATCH_QUEUE */
diff --git a/include/linux/security.h b/include/linux/security.h
index 910a1efa9a79..2ca2569bc12c 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1306,6 +1306,22 @@ static inline int security_post_notification(const struct cred *w_cred,
return 0;
}
#endif
+#if defined(CONFIG_SECURITY) && defined(CONFIG_MOUNT_NOTIFICATIONS)
+int security_watch_mount(struct watch *watch, struct path *path);
+#else
+static inline int security_watch_mount(struct watch *watch, struct path *path)
+{
+ return 0;
+}
+#endif
+#if defined(CONFIG_SECURITY) && defined(CONFIG_SB_NOTIFICATIONS)
+int security_watch_sb(struct watch *watch, struct super_block *sb);
+#else
+static inline int security_watch_sb(struct watch *watch, struct super_block *sb)
+{
+ return 0;
+}
+#endif

#ifdef CONFIG_SECURITY_NETWORK

diff --git a/security/security.c b/security/security.c
index db7b574c9c70..5c0463444a90 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2004,6 +2004,20 @@ int security_watch_key(struct key *key)
}
#endif

+#ifdef CONFIG_MOUNT_NOTIFICATIONS
+int security_watch_mount(struct watch *watch, struct path *path)
+{
+ return call_int_hook(watch_mount, 0, watch, path);
+}
+#endif
+
+#ifdef CONFIG_SB_NOTIFICATIONS
+int security_watch_sb(struct watch *watch, struct super_block *sb)
+{
+ return call_int_hook(watch_sb, 0, watch, sb);
+}
+#endif
+
#ifdef CONFIG_DEVICE_NOTIFICATIONS
int security_watch_devices(void)
{