diff --git a/drivers/mtd/ubi/debug.c b/drivers/mtd/ubi/debug.c
index d57f52bd2ff3..9ec3b8b6a0aa 100644
--- a/drivers/mtd/ubi/debug.c
+++ b/drivers/mtd/ubi/debug.c
@@ -598,9 +598,9 @@ int ubi_debugfs_init_dev(struct ubi_device *ubi)
 	if (!IS_ENABLED(CONFIG_DEBUG_FS))
 		return 0;
 
-	n = snprintf(d->dfs_dir_name, UBI_DFS_DIR_LEN + 1, UBI_DFS_DIR_NAME,
+	n = snprintf(d->dfs_dir_name, UBI_DFS_DIR_LEN, UBI_DFS_DIR_NAME,
 		     ubi->ubi_num);
-	if (n > UBI_DFS_DIR_LEN) {
+	if (n >= UBI_DFS_DIR_LEN) {
 		/* The array size is too small */
 		return -EINVAL;
 	}
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 1aead55090d0..1c9e874e8ede 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -420,7 +420,7 @@ struct ubi_debug_info {
 	unsigned int power_cut_min;
 	unsigned int power_cut_max;
 	unsigned int emulate_failures;
-	char dfs_dir_name[UBI_DFS_DIR_LEN + 1];
+	char dfs_dir_name[UBI_DFS_DIR_LEN];
 	struct dentry *dfs_dir;
 	struct dentry *dfs_chk_gen;
 	struct dentry *dfs_chk_io;
diff --git a/fs/ubifs/debug.c b/fs/ubifs/debug.c
index ac77ac1fd73e..d91cec93d968 100644
--- a/fs/ubifs/debug.c
+++ b/fs/ubifs/debug.c
@@ -2827,9 +2827,9 @@ void dbg_debugfs_init_fs(struct ubifs_info *c)
 	const char *fname;
 	struct ubifs_debug_info *d = c->dbg;
 
-	n = snprintf(d->dfs_dir_name, UBIFS_DFS_DIR_LEN + 1, UBIFS_DFS_DIR_NAME,
+	n = snprintf(d->dfs_dir_name, UBIFS_DFS_DIR_LEN, UBIFS_DFS_DIR_NAME,
 		     c->vi.ubi_num, c->vi.vol_id);
-	if (n > UBIFS_DFS_DIR_LEN) {
+	if (n >= UBIFS_DFS_DIR_LEN) {
 		/* The array size is too small */
 		return;
 	}
diff --git a/fs/ubifs/debug.h b/fs/ubifs/debug.h
index ed966108da80..d425861e6b82 100644
--- a/fs/ubifs/debug.h
+++ b/fs/ubifs/debug.h
@@ -19,10 +19,11 @@ typedef int (*dbg_znode_callback)(struct ubifs_info *c,
 
 /*
  * The UBIFS debugfs directory name pattern and maximum name length (3 for "ubi"
- * + 1 for "_" and plus 2x2 for 2 UBI numbers and 1 for the trailing zero byte.
+ * + 1 for "_" and 2 for UBI device numbers and 3 for volume number and 1 for
+ * the trailing zero byte.
  */
 #define UBIFS_DFS_DIR_NAME "ubi%d_%d"
-#define UBIFS_DFS_DIR_LEN  (3 + 1 + 2*2 + 1)
+#define UBIFS_DFS_DIR_LEN  (3 + 1 + 2 + 3 + 1)
 
 /**
  * ubifs_debug_info - per-FS debugging information.
@@ -103,7 +104,7 @@ struct ubifs_debug_info {
 	unsigned int chk_fs:1;
 	unsigned int tst_rcvry:1;
 
-	char dfs_dir_name[UBIFS_DFS_DIR_LEN + 1];
+	char dfs_dir_name[UBIFS_DFS_DIR_LEN];
 	struct dentry *dfs_dir;
 	struct dentry *dfs_dump_lprops;
 	struct dentry *dfs_dump_budg;
diff --git a/fs/ubifs/sysfs.c b/fs/ubifs/sysfs.c
index 1c958148bb87..aae32222f11b 100644
--- a/fs/ubifs/sysfs.c
+++ b/fs/ubifs/sysfs.c
@@ -91,17 +91,17 @@ static struct kset ubifs_kset = {
 int ubifs_sysfs_register(struct ubifs_info *c)
 {
 	int ret, n;
-	char dfs_dir_name[UBIFS_DFS_DIR_LEN+1];
+	char dfs_dir_name[UBIFS_DFS_DIR_LEN];
 
 	c->stats = kzalloc(sizeof(struct ubifs_stats_info), GFP_KERNEL);
 	if (!c->stats) {
 		ret = -ENOMEM;
 		goto out_last;
 	}
-	n = snprintf(dfs_dir_name, UBIFS_DFS_DIR_LEN + 1, UBIFS_DFS_DIR_NAME,
+	n = snprintf(dfs_dir_name, UBIFS_DFS_DIR_LEN, UBIFS_DFS_DIR_NAME,
 		     c->vi.ubi_num, c->vi.vol_id);
 
-	if (n > UBIFS_DFS_DIR_LEN) {
+	if (n >= UBIFS_DFS_DIR_LEN) {
 		/* The array size is too small */
 		ret = -EINVAL;
 		goto out_free;
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index b2c6554fa857..d69a5a42d693 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -157,13 +157,6 @@
 #define UBIFS_HMAC_ARR_SZ 0
 #endif
 
-/*
- * The UBIFS sysfs directory name pattern and maximum name length (3 for "ubi"
- * + 1 for "_" and plus 2x2 for 2 UBI numbers and 1 for the trailing zero byte.
- */
-#define UBIFS_DFS_DIR_NAME "ubi%d_%d"
-#define UBIFS_DFS_DIR_LEN  (3 + 1 + 2*2 + 1)
-
 /*
  * Lockdep classes for UBIFS inode @ui_mutex.
  */