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Subject[RFC PATCH 03/14] security: Add a hook for the point of notification insertion [ver #3]
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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 whoever set the watch.

(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 | 14 ++++++++++++++
include/linux/security.h | 14 ++++++++++++++
security/security.c | 9 +++++++++
3 files changed, 37 insertions(+)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 79d7c73676d7..16530255dc11 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1427,6 +1427,12 @@
* Check to see if a process is allowed to watch for event notifications
* from devices (as a global set).
*
+ * @post_notification:
+ * Check to see if a watch notification can be posted to a particular
+ * queue.
+ * @w_cred: The credentials of the whoever set the watch.
+ * @cred: The event-triggerer's credentials
+ * @n: The notification being posted
*
* Security hooks for using the eBPF maps and programs functionalities through
* eBPF syscalls.
@@ -1716,6 +1722,11 @@ union security_list_options {
#ifdef CONFIG_DEVICE_NOTIFICATIONS
int (*watch_devices)(void);
#endif
+#ifdef CONFIG_WATCH_QUEUE
+ int (*post_notification)(const struct cred *w_cred,
+ const struct cred *cred,
+ struct watch_notification *n);
+#endif

#ifdef CONFIG_SECURITY_NETWORK
int (*unix_stream_connect)(struct sock *sock, struct sock *other,
@@ -2009,6 +2020,9 @@ struct security_hook_heads {
#ifdef CONFIG_DEVICE_NOTIFICATIONS
struct hlist_head watch_devices;
#endif
+#ifdef CONFIG_WATCH_QUEUE
+ struct hlist_head post_notification;
+#endif /* CONFIG_WATCH_QUEUE */
#ifdef CONFIG_SECURITY_NETWORK
struct hlist_head unix_stream_connect;
struct hlist_head unix_may_send;
diff --git a/include/linux/security.h b/include/linux/security.h
index 8f2fa100d128..e03ee1164268 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -57,6 +57,8 @@ struct mm_struct;
struct fs_context;
struct fs_parameter;
enum fs_value_type;
+struct watch;
+struct watch_notification;

/* Default (no) options for the capable function */
#define CAP_OPT_NONE 0x0
@@ -1290,6 +1292,18 @@ static inline int security_watch_devices(void)
return 0;
}
#endif
+#if defined(CONFIG_SECURITY) && defined(CONFIG_WATCH_QUEUE)
+int security_post_notification(const struct cred *w_cred,
+ const struct cred *cred,
+ struct watch_notification *n);
+#else
+static inline int security_post_notification(const struct cred *w_cred,
+ const struct cred *cred,
+ struct watch_notification *n)
+{
+ return 0;
+}
+#endif

#ifdef CONFIG_SECURITY_NETWORK

diff --git a/security/security.c b/security/security.c
index 578863f230a6..9c1878a7fadf 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1956,6 +1956,15 @@ int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
}
EXPORT_SYMBOL(security_inode_getsecctx);

+#ifdef CONFIG_WATCH_QUEUE
+int security_post_notification(const struct cred *w_cred,
+ const struct cred *cred,
+ struct watch_notification *n)
+{
+ return call_int_hook(post_notification, 0, w_cred, cred, n);
+}
+#endif /* CONFIG_WATCH_QUEUE */
+
#ifdef CONFIG_KEY_NOTIFICATIONS
int security_watch_key(struct key *key)
{
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