1 files changed, 173 insertions, 149 deletions

diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c
index f6ff23fd101c..ddab9ea267d1 100644
--- a/fs/overlayfs/params.c
+++ b/fs/overlayfs/params.c
@@ -43,8 +43,10 @@ module_param_named(metacopy, ovl_metacopy_def, bool, 0644);
 MODULE_PARM_DESC(metacopy,
 		 "Default to on or off for the metadata only copy up feature");
 
-enum {
+enum ovl_opt {
 	Opt_lowerdir,
+	Opt_lowerdir_add,
+	Opt_datadir_add,
 	Opt_upperdir,
 	Opt_workdir,
 	Opt_default_permissions,
@@ -140,8 +142,11 @@ static int ovl_verity_mode_def(void)
 #define fsparam_string_empty(NAME, OPT) \
 	__fsparam(fs_param_is_string, NAME, OPT, fs_param_can_be_empty, NULL)
 
+
 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_flag("default_permissions", Opt_default_permissions),
@@ -238,19 +243,8 @@ static int ovl_mount_dir_noesc(const char *name, struct path *path)
 		pr_err("failed to resolve '%s': %i\n", name, err);
 		goto out;
 	}
-	err = -EINVAL;
-	if (ovl_dentry_weird(path->dentry)) {
-		pr_err("filesystem on '%s' not supported\n", name);
-		goto out_put;
-	}
-	if (!d_is_dir(path->dentry)) {
-		pr_err("'%s' not a directory\n", name);
-		goto out_put;
-	}
 	return 0;
 
-out_put:
-	path_put_init(path);
 out:
 	return err;
 }
@@ -268,7 +262,7 @@ static void ovl_unescape(char *s)
 	}
 }
 
-static int ovl_mount_dir(const char *name, struct path *path, bool upper)
+static int ovl_mount_dir(const char *name, struct path *path)
 {
 	int err = -ENOMEM;
 	char *tmp = kstrdup(name, GFP_KERNEL);
@@ -276,68 +270,147 @@ static int ovl_mount_dir(const char *name, struct path *path, bool upper)
 	if (tmp) {
 		ovl_unescape(tmp);
 		err = ovl_mount_dir_noesc(tmp, path);
-
-		if (!err && upper && path->dentry->d_flags & DCACHE_OP_REAL) {
-			pr_err("filesystem on '%s' not supported as upperdir\n",
-			       tmp);
-			path_put_init(path);
-			err = -EINVAL;
-		}
 		kfree(tmp);
 	}
 	return err;
 }
 
-static int ovl_parse_param_upperdir(const char *name, struct fs_context *fc,
-				    bool workdir)
+static int ovl_mount_dir_check(struct fs_context *fc, const struct path *path,
+			       enum ovl_opt layer, const char *name, bool upper)
 {
-	int err;
-	struct ovl_fs *ofs = fc->s_fs_info;
-	struct ovl_config *config = &ofs->config;
 	struct ovl_fs_context *ctx = fc->fs_private;
-	struct path path;
-	char *dup;
 
-	err = ovl_mount_dir(name, &path, true);
-	if (err)
-		return err;
+	if (ovl_dentry_weird(path->dentry))
+		return invalfc(fc, "filesystem on %s not supported", name);
+
+	if (!d_is_dir(path->dentry))
+		return invalfc(fc, "%s is not a directory", name);
+
 
 	/*
 	 * Check whether upper path is read-only here to report failures
 	 * early. Don't forget to recheck when the superblock is created
 	 * as the mount attributes could change.
 	 */
-	if (__mnt_is_readonly(path.mnt)) {
-		path_put(&path);
-		return -EINVAL;
+	if (upper) {
+		if (path->dentry->d_flags & DCACHE_OP_REAL)
+			return invalfc(fc, "filesystem on %s not supported as upperdir", name);
+		if (__mnt_is_readonly(path->mnt))
+			return invalfc(fc, "filesystem on %s is read-only", name);
+	} else {
+		if (ctx->lowerdir_all && layer != Opt_lowerdir)
+			return invalfc(fc, "lowerdir+ and datadir+ cannot follow lowerdir");
+		if (ctx->nr_data && layer == Opt_lowerdir_add)
+			return invalfc(fc, "regular lower layers cannot follow data layers");
+		if (ctx->nr == OVL_MAX_STACK)
+			return invalfc(fc, "too many lower directories, limit is %d",
+				       OVL_MAX_STACK);
 	}
+	return 0;
+}
 
-	dup = kstrdup(name, GFP_KERNEL);
-	if (!dup) {
-		path_put(&path);
+static int ovl_ctx_realloc_lower(struct fs_context *fc)
+{
+	struct ovl_fs_context *ctx = fc->fs_private;
+	struct ovl_fs_context_layer *l;
+	size_t nr;
+
+	if (ctx->nr < ctx->capacity)
+		return 0;
+
+	nr = min_t(size_t, max(4096 / sizeof(*l), ctx->capacity * 2),
+		   OVL_MAX_STACK);
+	l = krealloc_array(ctx->lower, nr, sizeof(*l), GFP_KERNEL_ACCOUNT);
+	if (!l)
 		return -ENOMEM;
+
+	ctx->lower = l;
+	ctx->capacity = nr;
+	return 0;
+}
+
+static void ovl_add_layer(struct fs_context *fc, enum ovl_opt layer,
+			 struct path *path, char **pname)
+{
+	struct ovl_fs *ofs = fc->s_fs_info;
+	struct ovl_config *config = &ofs->config;
+	struct ovl_fs_context *ctx = fc->fs_private;
+	struct ovl_fs_context_layer *l;
+
+	switch (layer) {
+	case Opt_workdir:
+		swap(config->workdir, *pname);
+		swap(ctx->work, *path);
+		break;
+	case Opt_upperdir:
+		swap(config->upperdir, *pname);
+		swap(ctx->upper, *path);
+		break;
+	case Opt_datadir_add:
+		ctx->nr_data++;
+		fallthrough;
+	case Opt_lowerdir_add:
+		WARN_ON(ctx->nr >= ctx->capacity);
+		l = &ctx->lower[ctx->nr++];
+		memset(l, 0, sizeof(*l));
+		swap(l->name, *pname);
+		swap(l->path, *path);
+		break;
+	default:
+		WARN_ON(1);
 	}
+}
 
-	if (workdir) {
-		kfree(config->workdir);
-		config->workdir = dup;
-		path_put(&ctx->work);
-		ctx->work = path;
-	} else {
-		kfree(config->upperdir);
-		config->upperdir = dup;
-		path_put(&ctx->upper);
-		ctx->upper = path;
+static int ovl_parse_layer(struct fs_context *fc, struct fs_parameter *param,
+			   enum ovl_opt layer)
+{
+	char *name = kstrdup(param->string, GFP_KERNEL);
+	bool upper = (layer == Opt_upperdir || layer == Opt_workdir);
+	struct path path;
+	int err;
+
+	if (!name)
+		return -ENOMEM;
+
+	if (upper)
+		err = ovl_mount_dir(name, &path);
+	else
+		err = ovl_mount_dir_noesc(name, &path);
+	if (err)
+		goto out_free;
+
+	err = ovl_mount_dir_check(fc, &path, layer, name, upper);
+	if (err)
+		goto out_put;
+
+	if (!upper) {
+		err = ovl_ctx_realloc_lower(fc);
+		if (err)
+			goto out_put;
 	}
-	return 0;
+
+	/* Store the user provided path string in ctx to show in mountinfo */
+	ovl_add_layer(fc, layer, &path, &name);
+
+out_put:
+	path_put(&path);
+out_free:
+	kfree(name);
+	return err;
 }
 
-static void ovl_parse_param_drop_lowerdir(struct ovl_fs_context *ctx)
+static void ovl_reset_lowerdirs(struct ovl_fs_context *ctx)
 {
-	for (size_t nr = 0; nr < ctx->nr; nr++) {
-		path_put(&ctx->lower[nr].path);
-		kfree(ctx->lower[nr].name);
-		ctx->lower[nr].name = NULL;
+	struct ovl_fs_context_layer *l = ctx->lower;
+
+	// Reset old user provided lowerdir string
+	kfree(ctx->lowerdir_all);
+	ctx->lowerdir_all = NULL;
+
+	for (size_t nr = 0; nr < ctx->nr; nr++, l++) {
+		path_put(&l->path);
+		kfree(l->name);
+		l->name = NULL;
 	}
 	ctx->nr = 0;
 	ctx->nr_data = 0;
@@ -346,7 +419,7 @@ static void ovl_parse_param_drop_lowerdir(struct ovl_fs_context *ctx)
 /*
  * Parse lowerdir= mount option:
  *
- * (1) lowerdir=/lower1:/lower2:/lower3::/data1::/data2
+ * e.g.: lowerdir=/lower1:/lower2:/lower3::/data1::/data2
  *     Set "/lower1", "/lower2", and "/lower3" as lower layers and
  *     "/data1" and "/data2" as data lower layers. Any existing lower
  *     layers are replaced.
@@ -356,9 +429,9 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 	int err;
 	struct ovl_fs_context *ctx = fc->fs_private;
 	struct ovl_fs_context_layer *l;
-	char *dup = NULL, *dup_iter;
+	char *dup = NULL, *iter;
 	ssize_t nr_lower = 0, nr = 0, nr_data = 0;
-	bool append = false, data_layer = false;
+	bool data_layer = false;
 
 	/*
 	 * Ensure we're backwards compatible with mount(2)
@@ -366,16 +439,21 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 	 */
 
 	/* drop all existing lower layers */
-	if (!*name) {
-		ovl_parse_param_drop_lowerdir(ctx);
+	ovl_reset_lowerdirs(ctx);
+
+	if (!*name)
 		return 0;
-	}
 
 	if (*name == ':') {
 		pr_err("cannot append lower layer");
 		return -EINVAL;
 	}
 
+	// Store user provided lowerdir string to show in mount options
+	ctx->lowerdir_all = kstrdup(name, GFP_KERNEL);
+	if (!ctx->lowerdir_all)
+		return -ENOMEM;
+
 	dup = kstrdup(name, GFP_KERNEL);
 	if (!dup)
 		return -ENOMEM;
@@ -385,36 +463,11 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 	if (nr_lower < 0)
 		goto out_err;
 
-	if ((nr_lower > OVL_MAX_STACK) ||
-	    (append && (size_add(ctx->nr, nr_lower) > OVL_MAX_STACK))) {
+	if (nr_lower > OVL_MAX_STACK) {
 		pr_err("too many lower directories, limit is %d\n", OVL_MAX_STACK);
 		goto out_err;
 	}
 
-	if (!append)
-		ovl_parse_param_drop_lowerdir(ctx);
-
-	/*
-	 * (1) append
-	 *
-	 * We want nr <= nr_lower <= capacity We know nr > 0 and nr <=
-	 * capacity. If nr == 0 this wouldn't be append. If nr +
-	 * nr_lower is <= capacity then nr <= nr_lower <= capacity
-	 * already holds. If nr + nr_lower exceeds capacity, we realloc.
-	 *
-	 * (2) replace
-	 *
-	 * Ensure we're backwards compatible with mount(2) which allows
-	 * "lowerdir=/a:/b:/c,lowerdir=/d:/e:/f" causing the last
-	 * specified lowerdir mount option to win.
-	 *
-	 * We want nr <= nr_lower <= capacity We know either (i) nr == 0
-	 * or (ii) nr > 0. We also know nr_lower > 0. The capacity
-	 * could've been changed multiple times already so we only know
-	 * nr <= capacity. If nr + nr_lower > capacity we realloc,
-	 * otherwise nr <= nr_lower <= capacity holds already.
-	 */
-	nr_lower += ctx->nr;
 	if (nr_lower > ctx->capacity) {
 		err = -ENOMEM;
 		l = krealloc_array(ctx->lower, nr_lower, sizeof(*ctx->lower),
@@ -426,41 +479,21 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 		ctx->capacity = nr_lower;
 	}
 
-	/*
-	 *   (3) By (1) and (2) we know nr <= nr_lower <= capacity.
-	 *   (4) If ctx->nr == 0 => replace
-	 *       We have verified above that the lowerdir mount option
-	 *       isn't an append, i.e., the lowerdir mount option
-	 *       doesn't start with ":" or "::".
-	 * (4.1) The lowerdir mount options only contains regular lower
-	 *       layers ":".
-	 *       => Nothing to verify.
-	 * (4.2) The lowerdir mount options contains regular ":" and
-	 *       data "::" layers.
-	 *       => We need to verify that data lower layers "::" aren't
-	 *          followed by regular ":" lower layers
-	 *   (5) If ctx->nr > 0 => append
-	 *       We know that there's at least one regular layer
-	 *       otherwise we would've failed when parsing the previous
-	 *       lowerdir mount option.
-	 * (5.1) The lowerdir mount option is a regular layer ":" append
-	 *       => We need to verify that no data layers have been
-	 *          specified before.
-	 * (5.2) The lowerdir mount option is a data layer "::" append
-	 *       We know that there's at least one regular layer or
-	 *       other data layers. => There's nothing to verify.
-	 */
-	dup_iter = dup;
-	for (nr = ctx->nr; nr < nr_lower; nr++) {
-		l = &ctx->lower[nr];
+	iter = dup;
+	l = ctx->lower;
+	for (nr = 0; nr < nr_lower; nr++, l++) {
 		memset(l, 0, sizeof(*l));
 
-		err = ovl_mount_dir(dup_iter, &l->path, false);
+		err = ovl_mount_dir(iter, &l->path);
+		if (err)
+			goto out_put;
+
+		err = ovl_mount_dir_check(fc, &l->path, Opt_lowerdir, iter, false);
 		if (err)
 			goto out_put;
 
 		err = -ENOMEM;
-		l->name = kstrdup(dup_iter, GFP_KERNEL_ACCOUNT);
+		l->name = kstrdup(iter, GFP_KERNEL_ACCOUNT);
 		if (!l->name)
 			goto out_put;
 
@@ -472,8 +505,8 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 			break;
 
 		err = -EINVAL;
-		dup_iter = strchr(dup_iter, '\0') + 1;
-		if (*dup_iter) {
+		iter = strchr(iter, '\0') + 1;
+		if (*iter) {
 			/*
 			 * This is a regular layer so we require that
 			 * there are no data layers.
@@ -489,7 +522,7 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 
 		/* This is a data lower layer. */
 		data_layer = true;
-		dup_iter++;
+		iter++;
 	}
 	ctx->nr = nr_lower;
 	ctx->nr_data += nr_data;
@@ -497,21 +530,7 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 	return 0;
 
 out_put:
-	/*
-	 * We know nr >= ctx->nr < nr_lower. If we failed somewhere
-	 * we want to undo until nr == ctx->nr. This is correct for
-	 * both ctx->nr == 0 and ctx->nr > 0.
-	 */
-	for (; nr >= ctx->nr; nr--) {
-		l = &ctx->lower[nr];
-		kfree(l->name);
-		l->name = NULL;
-		path_put(&l->path);
-
-		/* don't overflow */
-		if (nr == 0)
-			break;
-	}
+	ovl_reset_lowerdirs(ctx);
 
 out_err:
 	kfree(dup);
@@ -556,11 +575,11 @@ static int ovl_parse_param(struct fs_context *fc, struct fs_parameter *param)
 	case Opt_lowerdir:
 		err = ovl_parse_param_lowerdir(param->string, fc);
 		break;
+	case Opt_lowerdir_add:
+	case Opt_datadir_add:
 	case Opt_upperdir:
-		fallthrough;
 	case Opt_workdir:
-		err = ovl_parse_param_upperdir(param->string, fc,
-					       (Opt_workdir == opt));
+		err = ovl_parse_layer(fc, param, opt);
 		break;
 	case Opt_default_permissions:
 		config->default_permissions = true;
@@ -617,7 +636,7 @@ static int ovl_get_tree(struct fs_context *fc)
 
 static inline void ovl_fs_context_free(struct ovl_fs_context *ctx)
 {
-	ovl_parse_param_drop_lowerdir(ctx);
+	ovl_reset_lowerdirs(ctx);
 	path_put(&ctx->upper);
 	path_put(&ctx->work);
 	kfree(ctx->lower);
@@ -933,23 +952,28 @@ int ovl_show_options(struct seq_file *m, struct dentry *dentry)
 {
 	struct super_block *sb = dentry->d_sb;
 	struct ovl_fs *ofs = OVL_FS(sb);
-	size_t nr, nr_merged_lower = ofs->numlayer - ofs->numdatalayer;
+	size_t nr, nr_merged_lower, nr_lower = 0;
+	char **lowerdirs = ofs->config.lowerdirs;
 
 	/*
-	 * lowerdirs[] starts from offset 1, then
-	 * >= 0 regular lower layers prefixed with : and
-	 * >= 0 data-only lower layers prefixed with ::
-	 *
-	 * we need to escase comma and space like seq_show_option() does and
-	 * we also need to escape the colon separator from lowerdir paths.
+	 * lowerdirs[0] holds the colon separated list that user provided
+	 * with lowerdir mount option.
+	 * lowerdirs[1..numlayer] hold the lowerdir paths that were added
+	 * using the lowerdir+ and datadir+ mount options.
+	 * For now, we do not allow mixing the legacy lowerdir mount option
+	 * with the new lowerdir+ and datadir+ mount options.
 	 */
-	seq_puts(m, ",lowerdir=");
-	for (nr = 1; nr < ofs->numlayer; nr++) {
-		if (nr > 1)
-			seq_putc(m, ':');
-		if (nr >= nr_merged_lower)
-			seq_putc(m, ':');
-		seq_escape(m, ofs->config.lowerdirs[nr], ":, \t\n\\");
+	if (lowerdirs[0]) {
+		seq_show_option(m, "lowerdir", lowerdirs[0]);
+	} else {
+		nr_lower = ofs->numlayer;
+		nr_merged_lower = nr_lower - ofs->numdatalayer;
+	}
+	for (nr = 1; nr < nr_lower; nr++) {
+		if (nr < nr_merged_lower)
+			seq_show_option(m, "lowerdir+", lowerdirs[nr]);
+		else
+			seq_show_option(m, "datadir+", lowerdirs[nr]);
 	}
 	if (ofs->config.upperdir) {
 		seq_show_option(m, "upperdir", ofs->config.upperdir);