Merge tag 'vfs-6.13.ovl' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull overlayfs updates from Christian Brauner:
 "Make overlayfs support specifying layers through file descriptors.

  Currently overlayfs only allows specifying layers through path names.
  This is inconvenient for users that want to assemble an overlayfs
  mount purely based on file descriptors:

  This enables user to specify both:

    fsconfig(fd_overlay, FSCONFIG_SET_FD, "upperdir+", NULL, fd_upper);
    fsconfig(fd_overlay, FSCONFIG_SET_FD, "workdir+",  NULL, fd_work);
    fsconfig(fd_overlay, FSCONFIG_SET_FD, "lowerdir+", NULL, fd_lower1);
    fsconfig(fd_overlay, FSCONFIG_SET_FD, "lowerdir+", NULL, fd_lower2);

  in addition to:

    fsconfig(fd_overlay, FSCONFIG_SET_STRING, "upperdir+", "/upper",  0);
    fsconfig(fd_overlay, FSCONFIG_SET_STRING, "workdir+",  "/work",   0);
    fsconfig(fd_overlay, FSCONFIG_SET_STRING, "lowerdir+", "/lower1", 0);
    fsconfig(fd_overlay, FSCONFIG_SET_STRING, "lowerdir+", "/lower2", 0);

  There's also a large set of new overlayfs selftests to test new
  features and some older properties"

* tag 'vfs-6.13.ovl' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  selftests: add test for specifying 500 lower layers
  selftests: add overlayfs fd mounting selftests
  selftests: use shared header
  Documentation,ovl: document new file descriptor based layers
  ovl: specify layers via file descriptors
  fs: add helper to use mount option as path or fd

1 files changed, 91 insertions, 25 deletions

diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c
index e42546c6c5df..1115c22deca0 100644
--- a/fs/overlayfs/params.c
+++ b/fs/overlayfs/params.c
@@ -141,10 +141,10 @@ static int ovl_verity_mode_def(void)
 
 const struct fs_parameter_spec ovl_parameter_spec[] = {
 	fsparam_string_empty("lowerdir",    Opt_lowerdir),
-	fsparam_string("lowerdir+",         Opt_lowerdir_add),
-	fsparam_string("datadir+",          Opt_datadir_add),
-	fsparam_string("upperdir",          Opt_upperdir),
-	fsparam_string("workdir",           Opt_workdir),
+	fsparam_file_or_string("lowerdir+", Opt_lowerdir_add),
+	fsparam_file_or_string("datadir+",  Opt_datadir_add),
+	fsparam_file_or_string("upperdir",  Opt_upperdir),
+	fsparam_file_or_string("workdir",   Opt_workdir),
 	fsparam_flag("default_permissions", Opt_default_permissions),
 	fsparam_enum("redirect_dir",        Opt_redirect_dir, ovl_parameter_redirect_dir),
 	fsparam_enum("index",               Opt_index, ovl_parameter_bool),
@@ -367,40 +367,100 @@ static void ovl_add_layer(struct fs_context *fc, enum ovl_opt layer,
 	}
 }
 
-static int ovl_parse_layer(struct fs_context *fc, const char *layer_name, enum ovl_opt layer)
+static inline bool is_upper_layer(enum ovl_opt layer)
+{
+	return layer == Opt_upperdir || layer == Opt_workdir;
+}
+
+/* Handle non-file descriptor-based layer options that require path lookup. */
+static inline int ovl_kern_path(const char *layer_name, struct path *layer_path,
+				enum ovl_opt layer)
 {
-	char *name = kstrdup(layer_name, GFP_KERNEL);
-	bool upper = (layer == Opt_upperdir || layer == Opt_workdir);
-	struct path path;
 	int err;
 
+	switch (layer) {
+	case Opt_upperdir:
+		fallthrough;
+	case Opt_workdir:
+		fallthrough;
+	case Opt_lowerdir:
+		err = ovl_mount_dir(layer_name, layer_path);
+		break;
+	case Opt_lowerdir_add:
+		fallthrough;
+	case Opt_datadir_add:
+		err = ovl_mount_dir_noesc(layer_name, layer_path);
+		break;
+	default:
+		WARN_ON_ONCE(true);
+		err = -EINVAL;
+	}
+
+	return err;
+}
+
+static int ovl_do_parse_layer(struct fs_context *fc, const char *layer_name,
+			      struct path *layer_path, enum ovl_opt layer)
+{
+	char *name __free(kfree) = kstrdup(layer_name, GFP_KERNEL);
+	bool upper;
+	int err = 0;
+
 	if (!name)
 		return -ENOMEM;
 
-	if (upper || layer == Opt_lowerdir)
-		err = ovl_mount_dir(name, &path);
-	else
-		err = ovl_mount_dir_noesc(name, &path);
+	upper = is_upper_layer(layer);
+	err = ovl_mount_dir_check(fc, layer_path, layer, name, upper);
 	if (err)
-		goto out_free;
-
-	err = ovl_mount_dir_check(fc, &path, layer, name, upper);
-	if (err)
-		goto out_put;
+		return err;
 
 	if (!upper) {
 		err = ovl_ctx_realloc_lower(fc);
 		if (err)
-			goto out_put;
+			return err;
 	}
 
 	/* Store the user provided path string in ctx to show in mountinfo */
-	ovl_add_layer(fc, layer, &path, &name);
+	ovl_add_layer(fc, layer, layer_path, &name);
+	return err;
+}
+
+static int ovl_parse_layer(struct fs_context *fc, struct fs_parameter *param,
+			   enum ovl_opt layer)
+{
+	struct path layer_path __free(path_put) = {};
+	int err = 0;
+
+	switch (param->type) {
+	case fs_value_is_string:
+		err = ovl_kern_path(param->string, &layer_path, layer);
+		if (err)
+			return err;
+		err = ovl_do_parse_layer(fc, param->string, &layer_path, layer);
+		break;
+	case fs_value_is_file: {
+		char *buf __free(kfree);
+		char *layer_name;
+
+		buf = kmalloc(PATH_MAX, GFP_KERNEL_ACCOUNT);
+		if (!buf)
+			return -ENOMEM;
+
+		layer_path = param->file->f_path;
+		path_get(&layer_path);
+
+		layer_name = d_path(&layer_path, buf, PATH_MAX);
+		if (IS_ERR(layer_name))
+			return PTR_ERR(layer_name);
+
+		err = ovl_do_parse_layer(fc, layer_name, &layer_path, layer);
+		break;
+	}
+	default:
+		WARN_ON_ONCE(true);
+		err = -EINVAL;
+	}
 
-out_put:
-	path_put(&path);
-out_free:
-	kfree(name);
 	return err;
 }
 
@@ -474,7 +534,13 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 
 	iter = dup;
 	for (nr = 0; nr < nr_lower; nr++) {
-		err = ovl_parse_layer(fc, iter, Opt_lowerdir);
+		struct path path __free(path_put) = {};
+
+		err = ovl_kern_path(iter, &path, Opt_lowerdir);
+		if (err)
+			goto out_err;
+
+		err = ovl_do_parse_layer(fc, iter, &path, Opt_lowerdir);
 		if (err)
 			goto out_err;
 
@@ -555,7 +621,7 @@ static int ovl_parse_param(struct fs_context *fc, struct fs_parameter *param)
 	case Opt_datadir_add:
 	case Opt_upperdir:
 	case Opt_workdir:
-		err = ovl_parse_layer(fc, param->string, opt);
+		err = ovl_parse_layer(fc, param, opt);
 		break;
 	case Opt_default_permissions:
 		config->default_permissions = true;