1 files changed, 87 insertions, 2 deletions

diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index f976949d2634..fae1b6d397ea 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -193,7 +193,7 @@ static bool fsnotify_event_needs_parent(struct inode *inode, __u32 mnt_mask,
 	return mask & marks_mask;
 }
 
-/* Are there any inode/mount/sb objects that are interested in this event? */
+/* Are there any inode/mount/sb objects that watch for these events? */
 static inline bool fsnotify_object_watched(struct inode *inode, __u32 mnt_mask,
 					   __u32 mask)
 {
@@ -203,6 +203,24 @@ static inline bool fsnotify_object_watched(struct inode *inode, __u32 mnt_mask,
 	return mask & marks_mask & ALL_FSNOTIFY_EVENTS;
 }
 
+/* Report pre-content event with optional range info */
+int fsnotify_pre_content(const struct path *path, const loff_t *ppos,
+			 size_t count)
+{
+	struct file_range range;
+
+	/* Report page aligned range only when pos is known */
+	if (!ppos)
+		return fsnotify_path(path, FS_PRE_ACCESS);
+
+	range.path = path;
+	range.pos = PAGE_ALIGN_DOWN(*ppos);
+	range.count = PAGE_ALIGN(*ppos + count) - range.pos;
+
+	return fsnotify_parent(path->dentry, FS_PRE_ACCESS, &range,
+			       FSNOTIFY_EVENT_FILE_RANGE);
+}
+
 /*
  * Notify this dentry's parent about a child's events with child name info
  * if parent is watching or if inode/sb/mount are interested in events with
@@ -623,11 +641,78 @@ out:
 }
 EXPORT_SYMBOL_GPL(fsnotify);
 
+#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
+/*
+ * At open time we check fsnotify_sb_has_priority_watchers() and set the
+ * FMODE_NONOTIFY_ mode bits accordignly.
+ * Later, fsnotify permission hooks do not check if there are permission event
+ * watches, but that there were permission event watches at open time.
+ */
+void file_set_fsnotify_mode_from_watchers(struct file *file)
+{
+	struct dentry *dentry = file->f_path.dentry, *parent;
+	struct super_block *sb = dentry->d_sb;
+	__u32 mnt_mask, p_mask;
+
+	/* Is it a file opened by fanotify? */
+	if (FMODE_FSNOTIFY_NONE(file->f_mode))
+		return;
+
+	/*
+	 * Permission events is a super set of pre-content events, so if there
+	 * are no permission event watchers, there are also no pre-content event
+	 * watchers and this is implied from the single FMODE_NONOTIFY_PERM bit.
+	 */
+	if (likely(!fsnotify_sb_has_priority_watchers(sb,
+						FSNOTIFY_PRIO_CONTENT))) {
+		file_set_fsnotify_mode(file, FMODE_NONOTIFY_PERM);
+		return;
+	}
+
+	/*
+	 * If there are permission event watchers but no pre-content event
+	 * watchers, set FMODE_NONOTIFY | FMODE_NONOTIFY_PERM to indicate that.
+	 */
+	if ((!d_is_dir(dentry) && !d_is_reg(dentry)) ||
+	    likely(!fsnotify_sb_has_priority_watchers(sb,
+						FSNOTIFY_PRIO_PRE_CONTENT))) {
+		file_set_fsnotify_mode(file, FMODE_NONOTIFY | FMODE_NONOTIFY_PERM);
+		return;
+	}
+
+	/*
+	 * OK, there are some pre-content watchers. Check if anybody is
+	 * watching for pre-content events on *this* file.
+	 */
+	mnt_mask = READ_ONCE(real_mount(file->f_path.mnt)->mnt_fsnotify_mask);
+	if (unlikely(fsnotify_object_watched(d_inode(dentry), mnt_mask,
+				     FSNOTIFY_PRE_CONTENT_EVENTS))) {
+		/* Enable pre-content events */
+		file_set_fsnotify_mode(file, 0);
+		return;
+	}
+
+	/* Is parent watching for pre-content events on this file? */
+	if (dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED) {
+		parent = dget_parent(dentry);
+		p_mask = fsnotify_inode_watches_children(d_inode(parent));
+		dput(parent);
+		if (p_mask & FSNOTIFY_PRE_CONTENT_EVENTS) {
+			/* Enable pre-content events */
+			file_set_fsnotify_mode(file, 0);
+			return;
+		}
+	}
+	/* Nobody watching for pre-content events from this file */
+	file_set_fsnotify_mode(file, FMODE_NONOTIFY | FMODE_NONOTIFY_PERM);
+}
+#endif
+
 static __init int fsnotify_init(void)
 {
 	int ret;
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 23);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 24);
 
 	ret = init_srcu_struct(&fsnotify_mark_srcu);
 	if (ret)