linux-ext4 - [PATCH RFC 2/7] security: Add hooks to rule on setting a watch for superblock

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Date:   Tue, 20 Oct 2020 15:15:38 -0400
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     dhowells@...hat.com
Cc:     viro@...iv.linux.org.uk, tytso@....edu, khazhy@...gle.com,
        adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, kernel@...labora.com,
        Gabriel Krisman Bertazi <krisman@...labora.com>
Subject: [PATCH RFC 2/7] security: Add hooks to rule on setting a watch for superblock

From: David Howells <dhowells@...hat.com>

Add security hooks that will allow an LSM to rule on whether or not a watch
may be set for a supperblock.

Signed-off-by: David Howells <dhowells@...hat.com>
[Drop mount and key changes.  Rebase to mainline]
Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
---
 include/linux/lsm_hook_defs.h |  1 +
 include/linux/lsm_hooks.h     |  4 ++++
 include/linux/security.h      | 13 +++++++++++++
 security/security.c           |  7 +++++++
 4 files changed, 25 insertions(+)

diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 32a940117e7a..8fa8533598bc 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -261,6 +261,7 @@ LSM_HOOK(int, 0, inode_getsecctx, struct inode *inode, void **ctx,
 #if defined(CONFIG_SECURITY) && defined(CONFIG_WATCH_QUEUE)
 LSM_HOOK(int, 0, post_notification, const struct cred *w_cred,
 	 const struct cred *cred, struct watch_notification *n)
+LSM_HOOK(int, 0, watch_sb, struct super_block *sb)
 #endif /* CONFIG_SECURITY && CONFIG_WATCH_QUEUE */
 
 #if defined(CONFIG_SECURITY) && defined(CONFIG_KEY_NOTIFICATIONS)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 8814e3d5952d..325f50bea1ba 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1475,6 +1475,10 @@
  *	@w_cred: The credentials of the whoever set the watch.
  *	@cred: The event-triggerer's credentials
  *	@n: The notification being posted
+ * @watch_sb:
+ *	Check to see if a process is allowed to watch for event notifications
+ *	from a superblock.
+ *	@sb: The superblock to watch.
  *
  * @watch_key:
  *	Check to see if a process is allowed to watch for event notifications
diff --git a/include/linux/security.h b/include/linux/security.h
index bc2725491560..078e11a8872a 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -456,6 +456,11 @@ int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);
 int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);
 int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);
 int security_locked_down(enum lockdown_reason what);
+
+#ifdef CONFIG_WATCH_QUEUE
+int security_watch_sb(struct super_block *sb);
+#endif /* CONFIG_WATCH_QUEUE */
+
 #else /* CONFIG_SECURITY */
 
 static inline int call_blocking_lsm_notifier(enum lsm_event event, void *data)
@@ -1304,6 +1309,14 @@ static inline int security_locked_down(enum lockdown_reason what)
 {
 	return 0;
 }
+
+#ifdef CONFIG_WATCH_QUEUE
+static inline int security_watch_sb(struct super_block *sb)
+{
+	return 0;
+}
+#endif /* CONFIG_WATCH_QUEUE */
+
 #endif	/* CONFIG_SECURITY */
 
 #if defined(CONFIG_SECURITY) && defined(CONFIG_WATCH_QUEUE)
diff --git a/security/security.c b/security/security.c
index a28045dc9e7f..a5581aadc644 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2068,12 +2068,19 @@ 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);
 }
+
+int security_watch_sb(struct super_block *sb)
+{
+	return call_int_hook(watch_sb, 0, sb);
+}
+
 #endif /* CONFIG_WATCH_QUEUE */
 
 #ifdef CONFIG_KEY_NOTIFICATIONS
-- 
2.28.0