fsnotify: new fsnotify hooks and events types for access decisions

introduce a new fsnotify hook, fsnotify_perm(), which is called from the
security code.  This hook is used to allow fsnotify groups to make access
control decisions about events on the system.  We also must change the
generic fsnotify function to return an error code if we intend these hooks
to be in any way useful.

Signed-off-by: Eric Paris <eparis@redhat.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index b8cf161f5a6d..64efda9aae62 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -34,6 +34,25 @@ static inline void fsnotify_parent(struct path *path, struct dentry *dentry, __u
         __fsnotify_parent(path, dentry, mask);
 }
 
+/* simple call site for access decisions */
+static inline int fsnotify_perm(struct file *file, int mask)
+{
+        struct path *path = &file->f_path;
+        struct inode *inode = path->dentry->d_inode;
+        __u32 fsnotify_mask;
+
+        if (file->f_mode & FMODE_NONOTIFY)
+                return 0;
+        if (!(mask & (MAY_READ | MAY_OPEN)))
+                return 0;
+        if (mask & MAY_READ)
+                fsnotify_mask = FS_ACCESS_PERM;
+        if (mask & MAY_OPEN)
+                fsnotify_mask = FS_OPEN_PERM;
+
+        return fsnotify(inode, fsnotify_mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);
+}
+
 /*
  * fsnotify_d_move - dentry has been moved
  * Called with dcache_lock and dentry->d_lock held.