fanotify: store fsid in mark instead of in connector

Some filesystems like fuse and nfs have zero or non-unique fsid.
We would like to avoid reporting ambiguous fsid in events, so we need
to avoid marking objects with same fsid and different sb.

To make this easier to enforce, store the fsid in the marks of the group
instead of in the shared conenctor.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20231130165619.3386452-2-amir73il@gmail.com>

1 files changed, 8 insertions, 44 deletions

diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index c74ef947447d..d6944ff86ffa 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -537,8 +537,7 @@ int fsnotify_compare_groups(struct fsnotify_group *a, struct fsnotify_group *b)
 }
 
 static int fsnotify_attach_connector_to_object(fsnotify_connp_t *connp,
-					       unsigned int obj_type,
-					       __kernel_fsid_t *fsid)
+					       unsigned int obj_type)
 {
 	struct fsnotify_mark_connector *conn;
 
@@ -550,14 +549,7 @@ static int fsnotify_attach_connector_to_object(fsnotify_connp_t *connp,
 	conn->flags = 0;
 	conn->type = obj_type;
 	conn->obj = connp;
-	/* Cache fsid of filesystem containing the object */
-	if (fsid) {
-		conn->fsid = *fsid;
-		conn->flags = FSNOTIFY_CONN_FLAG_HAS_FSID;
-	} else {
-		conn->fsid.val[0] = conn->fsid.val[1] = 0;
-		conn->flags = 0;
-	}
+	conn->flags = 0;
 	fsnotify_get_sb_connectors(conn);
 
 	/*
@@ -608,8 +600,7 @@ out:
  */
 static int fsnotify_add_mark_list(struct fsnotify_mark *mark,
 				  fsnotify_connp_t *connp,
-				  unsigned int obj_type,
-				  int add_flags, __kernel_fsid_t *fsid)
+				  unsigned int obj_type, int add_flags)
 {
 	struct fsnotify_mark *lmark, *last = NULL;
 	struct fsnotify_mark_connector *conn;
@@ -619,41 +610,15 @@ static int fsnotify_add_mark_list(struct fsnotify_mark *mark,
 	if (WARN_ON(!fsnotify_valid_obj_type(obj_type)))
 		return -EINVAL;
 
-	/* Backend is expected to check for zero fsid (e.g. tmpfs) */
-	if (fsid && WARN_ON_ONCE(!fsid->val[0] && !fsid->val[1]))
-		return -ENODEV;
-
 restart:
 	spin_lock(&mark->lock);
 	conn = fsnotify_grab_connector(connp);
 	if (!conn) {
 		spin_unlock(&mark->lock);
-		err = fsnotify_attach_connector_to_object(connp, obj_type,
-							  fsid);
+		err = fsnotify_attach_connector_to_object(connp, obj_type);
 		if (err)
 			return err;
 		goto restart;
-	} else if (fsid && !(conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID)) {
-		conn->fsid = *fsid;
-		/* Pairs with smp_rmb() in fanotify_get_fsid() */
-		smp_wmb();
-		conn->flags |= FSNOTIFY_CONN_FLAG_HAS_FSID;
-	} else if (fsid && (conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID) &&
-		   (fsid->val[0] != conn->fsid.val[0] ||
-		    fsid->val[1] != conn->fsid.val[1])) {
-		/*
-		 * Backend is expected to check for non uniform fsid
-		 * (e.g. btrfs), but maybe we missed something?
-		 * Only allow setting conn->fsid once to non zero fsid.
-		 * inotify and non-fid fanotify groups do not set nor test
-		 * conn->fsid.
-		 */
-		pr_warn_ratelimited("%s: fsid mismatch on object of type %u: "
-				    "%x.%x != %x.%x\n", __func__, conn->type,
-				    fsid->val[0], fsid->val[1],
-				    conn->fsid.val[0], conn->fsid.val[1]);
-		err = -EXDEV;
-		goto out_err;
 	}
 
 	/* is mark the first mark? */
@@ -703,7 +668,7 @@ out_err:
  */
 int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
 			     fsnotify_connp_t *connp, unsigned int obj_type,
-			     int add_flags, __kernel_fsid_t *fsid)
+			     int add_flags)
 {
 	struct fsnotify_group *group = mark->group;
 	int ret = 0;
@@ -723,7 +688,7 @@ int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
 	fsnotify_get_mark(mark); /* for g_list */
 	spin_unlock(&mark->lock);
 
-	ret = fsnotify_add_mark_list(mark, connp, obj_type, add_flags, fsid);
+	ret = fsnotify_add_mark_list(mark, connp, obj_type, add_flags);
 	if (ret)
 		goto err;
 
@@ -742,14 +707,13 @@ err:
 }
 
 int fsnotify_add_mark(struct fsnotify_mark *mark, fsnotify_connp_t *connp,
-		      unsigned int obj_type, int add_flags,
-		      __kernel_fsid_t *fsid)
+		      unsigned int obj_type, int add_flags)
 {
 	int ret;
 	struct fsnotify_group *group = mark->group;
 
 	fsnotify_group_lock(group);
-	ret = fsnotify_add_mark_locked(mark, connp, obj_type, add_flags, fsid);
+	ret = fsnotify_add_mark_locked(mark, connp, obj_type, add_flags);
 	fsnotify_group_unlock(group);
 	return ret;
 }