[PATCH v2 06/10] fanotify: gate fs event classification by group type

[Amir Goldstein <amir73il@gmail.com>]

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 fs 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 fs events check inside fanotify_alloc_fs_watcher_event()
are already properly gated.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/notify/fanotify/fanotify.c | 73 ++++++++++++++++++++++++++++-------
 1 file changed, 58 insertions(+), 15 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 80116026d3ae0..987092c38789b 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -744,11 +744,12 @@ static struct fanotify_event *fanotify_alloc_error_event(
 	return &fee->fae;
 }
 
-static struct fanotify_event *fanotify_alloc_event(
+static struct fanotify_event *fanotify_alloc_fs_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)
 {
 	struct fanotify_event *event = NULL;
 	gfp_t gfp = GFP_KERNEL_ACCOUNT;
@@ -759,14 +760,11 @@ 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) {
 		/*
@@ -848,22 +846,69 @@ static struct fanotify_event *fanotify_alloc_event(
 	if (fanotify_is_fs_perm_event(group, mask)) {
 		event = fanotify_alloc_perm_event(data, data_type, gfp);
 	} else if (fs_error) {
-		event = fanotify_alloc_error_event(group, fsid, fs_error, &hash);
+		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);
+						  moved, hash, gfp);
 	} else if (fid_mode) {
-		event = fanotify_alloc_fid_event(id, fsid, &hash, gfp);
+		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_path_event(path, hash, gfp);
+	} else {
+		WARN_ON_ONCE(1);
+	}
+
+	set_active_memcg(old_memcg);
+	return event;
+}
+
+static struct fanotify_event *fanotify_alloc_ns_watcher_event(
+				struct fsnotify_group *group, u64 mask,
+				const void *data, int data_type)
+{
+	u64 mnt_id = fsnotify_data_mnt_id(data, data_type);
+	struct mem_cgroup *old_memcg;
+	struct fanotify_event *event = NULL;
+	gfp_t gfp = GFP_KERNEL_ACCOUNT;
+
+	if (group->max_events == UINT_MAX)
+		gfp |= __GFP_NOFAIL;
+	else
+		gfp |= __GFP_RETRY_MAYFAIL;
+
+	old_memcg = set_active_memcg(group->memcg);
+
+	if (mnt_id) {
 		event = fanotify_alloc_mnt_event(mnt_id, gfp);
 	} else {
 		WARN_ON_ONCE(1);
 	}
 
+	set_active_memcg(old_memcg);
+	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;
+	unsigned int hash = 0;
+	bool ondir = mask & FAN_ONDIR;
+	struct pid *pid;
+
+	if (fsnotify_is_ns_watcher(group)) {
+		event = fanotify_alloc_ns_watcher_event(group, mask, data,
+							data_type);
+	} else {
+		event = fanotify_alloc_fs_watcher_event(group, mask, data,
+						data_type, dir, name, fsid,
+						match_mask, &hash);
+	}
 	if (!event)
-		goto out;
+		return NULL;
 
 	if (FAN_GROUP_FLAG(group, FAN_REPORT_TID))
 		pid = get_pid(task_pid(current));
@@ -875,8 +920,6 @@ static struct fanotify_event *fanotify_alloc_event(
 	fanotify_init_event(event, hash, mask);
 	event->pid = pid;
 
-out:
-	set_active_memcg(old_memcg);
 	return event;
 }
 
@@ -966,8 +1009,8 @@ 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);
 
 	bool is_perm = fanotify_is_fs_perm_event(group, mask);
 	if (is_perm) {
-- 
2.54.0