[PATCH 04/13] security: Add a hook for the point of notification insertion [ver #4]

David Howells
2019-06-07T14:18:13Z

Add a security hook that allows an LSM to rule on whether a notification
message is allowed to be inserted into a particular watch queue.

The hook is given the following information:

(1) The credentials of the triggerer (which may be init_cred for a system
notification, eg. a hardware error).

(2) The credentials of the creator of the watch buffer.

(3) The notification message.

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 | 10 ++++++++++
include/linux/security.h | 10 ++++++++++
security/security.c | 6 ++++++
3 files changed, 26 insertions(+)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 0543449c0f6e..94fb6067fed5 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1445,6 +1445,12 @@
* from devices (as a global set).
* @watch: The watch object
*
+ * @post_notification:
+ * Check to see if a watch notification can be posted to a particular
+ * queue.
+ * @q_cred: The credentials of the target watch queue.
+ * @cred: The event-triggerer's credentials
+ * @n: The notification being posted
*
* Security hooks for using the eBPF maps and programs functionalities through
* eBPF syscalls.
@@ -1729,6 +1735,9 @@ union security_list_options {
int (*watch_sb)(struct watch *watch, struct super_block *sb);
int (*watch_key)(struct watch *watch, struct key *key);
int (*watch_devices)(struct watch *watch);
+ int (*post_notification)(const struct cred *q_cred,
+ const struct cred *cred,
+ struct watch_notification *n);
#endif /* CONFIG_WATCH_QUEUE */

#ifdef CONFIG_SECURITY_NETWORK
@@ -2014,6 +2023,7 @@ struct security_hook_heads {
struct hlist_head watch_sb;
struct hlist_head watch_key;
struct hlist_head watch_devices;
+ struct hlist_head post_notification;
#endif /* CONFIG_WATCH_QUEUE */
#ifdef CONFIG_SECURITY_NETWORK
struct hlist_head unix_stream_connect;
diff --git a/include/linux/security.h b/include/linux/security.h
index ac3bf6b5f87b..ed301edeaa19 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -59,6 +59,7 @@ struct fs_parameter;
enum fs_value_type;
struct fsinfo_kparams;
struct watch;
+struct watch_notification;

/* Default (no) options for the capable function */
#define CAP_OPT_NONE 0x0
@@ -402,6 +403,9 @@ int security_watch_mount(struct watch *watch, struct path *path);
int security_watch_sb(struct watch *watch, struct super_block *sb);
int security_watch_key(struct watch *watch, struct key *key);
int security_watch_devices(struct watch *watch);
+int security_post_notification(const struct cred *q_cred,
+ const struct cred *cred,
+ struct watch_notification *n);
#endif /* CONFIG_WATCH_QUEUE */
#else /* CONFIG_SECURITY */

@@ -1239,6 +1243,12 @@ static inline int security_watch_devices(struct watch *watch)
{
return 0;
}
+static inline int security_post_notification(const struct cred *q_cred,
+ const struct cred *cred,
+ struct watch_notification *n)
+{
+ return 0;
+}
#endif /* CONFIG_WATCH_QUEUE */
#endif /* CONFIG_SECURITY */

diff --git a/security/security.c b/security/security.c
index ee2f8539a0d5..8a04ac74b4fe 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1950,6 +1950,12 @@ int security_watch_devices(struct watch *watch)
return call_int_hook(watch_devices, 0, watch);
}

+int security_post_notification(const struct cred *q_cred,
+ const struct cred *cred,
+ struct watch_notification *n)
+{
+ return call_int_hook(post_notification, 0, q_cred, cred, n);
+}
#endif /* CONFIG_WATCH_QUEUE */

#ifdef CONFIG_SECURITY_NETWORK