diff --git a/module/os/freebsd/zfs/zfs_vnops_os.c b/module/os/freebsd/zfs/zfs_vnops_os.c
index be773190e02a..93ec05806516 100644
--- a/module/os/freebsd/zfs/zfs_vnops_os.c
+++ b/module/os/freebsd/zfs/zfs_vnops_os.c
@@ -5190,25 +5190,28 @@ zfs_check_attrname(const char *name)
 }
 
 static char *
-zfs_attrname_maybe_rename(char *name)
+zfs_dup_attrname_maybe_rename(const char *name)
 {
-	char *ret = name;
+	char *ret;
+	size_t len = strlen(name);
 
 	if (zfs_xattr_compat)
 		return (ret);
 
 	if (ZFS_XA_NS_PREFIX_FORBIDDEN(name)) {
-		ret = kmem_alloc(strlen(name) + 6, KM_SLEEP);
-		snprintf(ret, strlen(name), "user.%s", name);
+		ret = kmem_alloc(len + 6, KM_SLEEP);
+		snprintf(ret, len + 5, "user.%s", name);
 	}
+
+	ret = kmem_alloc(len + 1, KM_SLEEP);
+	memcpy(ret, name, len);
 	return (ret);
 }
 
 static void
-zfs_attrname_maybe_free(char *name, char *orig)
+zfs_dup_attrname_free(char *name, const char *orig)
 {
-	if (name != orig)
-		kmem_free(name, strlen(name));
+	kmem_free(name, strlen(name));
 }
 
 /*
@@ -5413,16 +5416,16 @@ zfs_getextattr(struct vop_getextattr_args *ap)
 	if (error != 0)
 		return (SET_ERROR(error));
 
-	maybe_renamed = zfs_attrname_maybe_rename(origname);
+	maybe_renamed = zfs_dup_attrname_maybe_rename(origname);
 
 	error = zfs_check_attrname(maybe_renamed);
 	if (error != 0) {
-		zfs_attrname_maybe_free(maybe_renamed, origname);
+		zfs_dup_attrname_free(maybe_renamed, origname);
 		return (error);
 	}
 
 	if ((error = zfs_enter_verify_zp(zfsvfs, zp, FTAG)) != 0) {
-		zfs_attrname_maybe_free(maybe_renamed, origname);
+		zfs_dup_attrname_free(maybe_renamed, origname);
 		return (error);
 	}
 	error = ENOENT;
@@ -5442,7 +5445,7 @@ zfs_getextattr(struct vop_getextattr_args *ap)
 	zfs_exit(zfsvfs, FTAG);
 	if (error == ENOENT)
 		error = SET_ERROR(ENOATTR);
-	zfs_attrname_maybe_free(maybe_renamed, origname);
+	zfs_dup_attrname_free(maybe_renamed, origname);
 	return (error);
 }
 
@@ -5564,14 +5567,14 @@ zfs_deleteextattr(struct vop_deleteextattr_args *ap)
 	if (error != 0)
 		return (SET_ERROR(error));
 
-	maybe_renamed = zfs_attrname_maybe_rename(origname);
+	maybe_renamed = zfs_dup_attrname_maybe_rename(origname);
 	error = zfs_check_attrname(maybe_renamed);
 	if (error != 0) {
-		zfs_attrname_maybe_free(maybe_renamed, origname);
+		zfs_dup_attrname_free(maybe_renamed, origname);
 		return (error);
 	}
 	if ((error = zfs_enter_verify_zp(zfsvfs, zp, FTAG)) != 0) {
-		zfs_attrname_maybe_free(maybe_renamed, origname);
+		zfs_dup_attrname_free(maybe_renamed, origname);
 		return (error);
 	}
 	rw_enter(&zp->z_xattr_lock, RW_WRITER);
@@ -5591,7 +5594,7 @@ zfs_deleteextattr(struct vop_deleteextattr_args *ap)
 	zfs_exit(zfsvfs, FTAG);
 	if (error == ENOENT)
 		error = SET_ERROR(ENOATTR);
-	zfs_attrname_maybe_free(maybe_renamed, origname);
+	zfs_dup_attrname_free(maybe_renamed, origname);
 	return (error);
 }
 
@@ -5761,15 +5764,15 @@ zfs_setextattr(struct vop_setextattr_args *ap)
 	if (error != 0)
 		return (SET_ERROR(error));
 
-	maybe_renamed = zfs_attrname_maybe_rename(origname);
+	maybe_renamed = zfs_dup_attrname_maybe_rename(origname);
 	error = zfs_check_attrname(maybe_renamed);
 	if (error != 0) {
-		zfs_attrname_maybe_free(maybe_renamed, origname);
+		zfs_dup_attrname_free(maybe_renamed, origname);
 		return (error);
 	}
 
 	if ((error = zfs_enter_verify_zp(zfsvfs, zp, FTAG)) != 0) {
-		zfs_attrname_maybe_free(maybe_renamed, origname);
+		zfs_dup_attrname_free(maybe_renamed, origname);
 		return (error);
 	}
 	rw_enter(&zp->z_xattr_lock, RW_WRITER);
@@ -5778,7 +5781,7 @@ zfs_setextattr(struct vop_setextattr_args *ap)
 
 	rw_exit(&zp->z_xattr_lock);
 	zfs_exit(zfsvfs, FTAG);
-	zfs_attrname_maybe_free(maybe_renamed, origname);
+	zfs_dup_attrname_free(maybe_renamed, origname);
 	return (error);
 }