fanotify decides on how to allocate events based on the event mask.
The event mask bits that correspond to filesystem watchers are only
meaningful in the context of filesystem group type.

Hence, before checking if event is a specific filesystem event (e.g.
FS_RENAME) need to first check the group type is filesystem.

Separate fanotify_alloc_event() into an allocator per group type, so
that all the filesystem event checks inside
fanotify_alloc_filesystem_watcher_event() are already properly gated.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/notify/fanotify/fanotify.c | 88 ++++++++++++++++++++++++-----------
 1 file changed, 60 insertions(+), 28 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 9dc39b16a41a7..35b87a7cc6129 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -745,14 +745,14 @@ static struct fanotify_event *fanotify_alloc_error_event(
 	return &fee->fae;
 }
 
-static struct fanotify_event *fanotify_alloc_event(
+static struct fanotify_event *fanotify_alloc_filesystem_watcher_event(
 				struct fsnotify_group *group,
 				u32 mask, const void *data, int data_type,
 				struct inode *dir, const struct qstr *file_name,
-				__kernel_fsid_t *fsid, u32 match_mask)
+				__kernel_fsid_t *fsid, u32 match_mask,
+				unsigned int *hash, gfp_t gfp)
 {
 	struct fanotify_event *event = NULL;
-	gfp_t gfp = GFP_KERNEL_ACCOUNT;
 	unsigned int fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);
 	struct inode *id = fanotify_fid_inode(mask, data, data_type, dir,
 					      fid_mode);
@@ -760,14 +760,10 @@ static struct fanotify_event *fanotify_alloc_event(
 	const struct path *path = fsnotify_data_path(data, data_type);
 	struct fs_error_report *fs_error =
 		fsnotify_data_error_report(data, data_type);
-	u64 mnt_id = fsnotify_data_mnt_id(data, data_type);
-	struct mem_cgroup *old_memcg;
 	struct dentry *moved = NULL;
 	struct inode *child = NULL;
 	bool name_event = false;
-	unsigned int hash = 0;
 	bool ondir = mask & FAN_ONDIR;
-	struct pid *pid;
 
 	if ((fid_mode & FAN_REPORT_DIR_FID) && dirid) {
 		/*
@@ -832,6 +828,54 @@ static struct fanotify_event *fanotify_alloc_event(
 		}
 	}
 
+	if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS) &&
+	    mask & FANOTIFY_PERM_EVENTS) {
+		event = fanotify_alloc_perm_event(data, data_type, gfp);
+	} else if (fs_error) {
+		event = fanotify_alloc_error_event(group, fsid, fs_error,
+						   hash);
+	} else if (name_event && (file_name || moved || child)) {
+		event = fanotify_alloc_name_event(dirid, fsid, file_name, child,
+						  moved, hash, gfp);
+	} else if (fid_mode) {
+		event = fanotify_alloc_fid_event(id, fsid, hash, gfp);
+	} else if (path) {
+		event = fanotify_alloc_path_event(path, hash, gfp);
+	} else {
+		WARN_ON_ONCE(1);
+	}
+
+	return event;
+}
+
+static struct fanotify_event *fanotify_alloc_namespace_watcher_event(
+				struct fsnotify_group *group, u64 mask,
+				const void *data, int data_type, gfp_t gfp)
+{
+	u64 mnt_id = fsnotify_data_mnt_id(data, data_type);
+	struct fanotify_event *event = NULL;
+
+	if (mnt_id)
+		event = fanotify_alloc_mnt_event(mnt_id, gfp);
+	else
+		WARN_ON_ONCE(1);
+
+	return event;
+}
+
+static struct fanotify_event *fanotify_alloc_event(
+				struct fsnotify_group *group, u64 mask,
+				const void *data, int data_type,
+				struct inode *dir, const struct qstr *name,
+				__kernel_fsid_t *fsid, u32 match_mask)
+{
+	struct fanotify_event *event = NULL;
+	gfp_t gfp = GFP_KERNEL_ACCOUNT;
+	struct mem_cgroup *old_memcg;
+	unsigned int hash = 0;
+	bool ondir = mask & FAN_ONDIR;
+	struct pid *pid;
+
 	/*
 	 * For queues with unlimited length lost events are not expected and
 	 * can possibly have security implications. Avoid losing events when
@@ -855,25 +899,13 @@ static struct fanotify_event *fanotify_alloc_event(
 	    pidfs_register_pid_gfp(pid, gfp))
 		goto out;
 
-	if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS) &&
-	    mask & FANOTIFY_PERM_EVENTS) {
-		event = fanotify_alloc_perm_event(data, data_type, gfp);
-	} else if (fs_error) {
-		event = fanotify_alloc_error_event(group, fsid, fs_error,
-						   &hash);
-	} else if (name_event && (file_name || moved || child)) {
-		event = fanotify_alloc_name_event(dirid, fsid, file_name, child,
-						  moved, &hash, gfp);
-	} else if (fid_mode) {
-		event = fanotify_alloc_fid_event(id, fsid, &hash, gfp);
-	} else if (path) {
-		event = fanotify_alloc_path_event(path, &hash, gfp);
-	} else if (mnt_id) {
-		event = fanotify_alloc_mnt_event(mnt_id, gfp);
-	} else {
-		WARN_ON_ONCE(1);
-	}
-
+	if (fsnotify_is_namespace_watcher(group))
+		event = fanotify_alloc_namespace_watcher_event(group, mask,
+							data, data_type, gfp);
+	else
+		event = fanotify_alloc_filesystem_watcher_event(group, mask,
+						data, data_type, dir, name,
+						fsid, match_mask, &hash, gfp);
 	if (!event)
 		goto out;
 
@@ -975,8 +1007,8 @@ static int fanotify_handle_event(struct fsnotify_group *group, u32 mask,
 	if (!mask)
 		return 0;
 
-	pr_debug("%s: group=%p mask=%x report_mask=%x\n", __func__,
-		 group, mask, match_mask);
+	pr_debug("%s: group=%p type=%d mask=%x report_mask=%x\n", __func__,
+		 group, group->type, mask, match_mask);
 
 	if (is_perm_event) {
 		/*
-- 
2.55.0