Merge tag 'ovl-fixes-6.6-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/overlayfs/vfs

Pull overlayfs fixes from Amir Goldstein:

 - Various fixes for regressions due to conversion to new mount
   api in v6.5

 - Disable a new mount option syntax (append lowerdir) that was
   added in v6.5 because we plan to add a different lowerdir
   append syntax in v6.7

* tag 'ovl-fixes-6.6-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/overlayfs/vfs:
  ovl: temporarily disable appending lowedirs
  ovl: fix regression in showing lowerdir mount option
  ovl: fix regression in parsing of mount options with escaped comma
  fs: factor out vfs_parse_monolithic_sep() helper

2 files changed, 84 insertions, 69 deletions

diff --git a/fs/fs_context.c b/fs/fs_context.c
index a0ad7a0c4680..98589aae5208 100644
--- a/fs/fs_context.c
+++ b/fs/fs_context.c
@@ -192,17 +192,19 @@ int vfs_parse_fs_string(struct fs_context *fc, const char *key,
 EXPORT_SYMBOL(vfs_parse_fs_string);
 
 /**
- * generic_parse_monolithic - Parse key[=val][,key[=val]]* mount data
+ * vfs_parse_monolithic_sep - Parse key[=val][,key[=val]]* mount data
  * @fc: The superblock configuration to fill in.
  * @data: The data to parse
+ * @sep: callback for separating next option
  *
- * Parse a blob of data that's in key[=val][,key[=val]]* form.  This can be
- * called from the ->monolithic_mount_data() fs_context operation.
+ * Parse a blob of data that's in key[=val][,key[=val]]* form with a custom
+ * option separator callback.
  *
  * Returns 0 on success or the error returned by the ->parse_option() fs_context
  * operation on failure.
  */
-int generic_parse_monolithic(struct fs_context *fc, void *data)
+int vfs_parse_monolithic_sep(struct fs_context *fc, void *data,
+			     char *(*sep)(char **))
 {
 	char *options = data, *key;
 	int ret = 0;
@@ -214,7 +216,7 @@ int generic_parse_monolithic(struct fs_context *fc, void *data)
 	if (ret)
 		return ret;
 
-	while ((key = strsep(&options, ",")) != NULL) {
+	while ((key = sep(&options)) != NULL) {
 		if (*key) {
 			size_t v_len = 0;
 			char *value = strchr(key, '=');
@@ -233,6 +235,28 @@ int generic_parse_monolithic(struct fs_context *fc, void *data)
 
 	return ret;
 }
+EXPORT_SYMBOL(vfs_parse_monolithic_sep);
+
+static char *vfs_parse_comma_sep(char **s)
+{
+	return strsep(s, ",");
+}
+
+/**
+ * generic_parse_monolithic - Parse key[=val][,key[=val]]* mount data
+ * @fc: The superblock configuration to fill in.
+ * @data: The data to parse
+ *
+ * Parse a blob of data that's in key[=val][,key[=val]]* form.  This can be
+ * called from the ->monolithic_mount_data() fs_context operation.
+ *
+ * Returns 0 on success or the error returned by the ->parse_option() fs_context
+ * operation on failure.
+ */
+int generic_parse_monolithic(struct fs_context *fc, void *data)
+{
+	return vfs_parse_monolithic_sep(fc, data, vfs_parse_comma_sep);
+}
 EXPORT_SYMBOL(generic_parse_monolithic);
 
 /**
diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c
index 95b751507ac8..f6ff23fd101c 100644
--- a/fs/overlayfs/params.c
+++ b/fs/overlayfs/params.c
@@ -157,6 +157,34 @@ const struct fs_parameter_spec ovl_parameter_spec[] = {
 	{}
 };
 
+static char *ovl_next_opt(char **s)
+{
+	char *sbegin = *s;
+	char *p;
+
+	if (sbegin == NULL)
+		return NULL;
+
+	for (p = sbegin; *p; p++) {
+		if (*p == '\\') {
+			p++;
+			if (!*p)
+				break;
+		} else if (*p == ',') {
+			*p = '\0';
+			*s = p + 1;
+			return sbegin;
+		}
+	}
+	*s = NULL;
+	return sbegin;
+}
+
+static int ovl_parse_monolithic(struct fs_context *fc, void *data)
+{
+	return vfs_parse_monolithic_sep(fc, data, ovl_next_opt);
+}
+
 static ssize_t ovl_parse_param_split_lowerdirs(char *str)
 {
 	ssize_t nr_layers = 1, nr_colons = 0;
@@ -164,7 +192,8 @@ static ssize_t ovl_parse_param_split_lowerdirs(char *str)
 
 	for (s = d = str;; s++, d++) {
 		if (*s == '\\') {
-			s++;
+			/* keep esc chars in split lowerdir */
+			*d++ = *s++;
 		} else if (*s == ':') {
 			bool next_colon = (*(s + 1) == ':');
 
@@ -239,7 +268,7 @@ static void ovl_unescape(char *s)
 	}
 }
 
-static int ovl_mount_dir(const char *name, struct path *path)
+static int ovl_mount_dir(const char *name, struct path *path, bool upper)
 {
 	int err = -ENOMEM;
 	char *tmp = kstrdup(name, GFP_KERNEL);
@@ -248,7 +277,7 @@ static int ovl_mount_dir(const char *name, struct path *path)
 		ovl_unescape(tmp);
 		err = ovl_mount_dir_noesc(tmp, path);
 
-		if (!err && path->dentry->d_flags & DCACHE_OP_REAL) {
+		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);
@@ -269,7 +298,7 @@ static int ovl_parse_param_upperdir(const char *name, struct fs_context *fc,
 	struct path path;
 	char *dup;
 
-	err = ovl_mount_dir(name, &path);
+	err = ovl_mount_dir(name, &path, true);
 	if (err)
 		return err;
 
@@ -321,12 +350,6 @@ static void ovl_parse_param_drop_lowerdir(struct ovl_fs_context *ctx)
  *     Set "/lower1", "/lower2", and "/lower3" as lower layers and
  *     "/data1" and "/data2" as data lower layers. Any existing lower
  *     layers are replaced.
- * (2) lowerdir=:/lower4
- *     Append "/lower4" to current stack of lower layers. This requires
- *     that there already is at least one lower layer configured.
- * (3) lowerdir=::/lower5
- *     Append data "/lower5" as data lower layer. This requires that
- *     there's at least one regular lower layer present.
  */
 static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 {
@@ -348,49 +371,9 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 		return 0;
 	}
 
-	if (strncmp(name, "::", 2) == 0) {
-		/*
-		 * This is a data layer.
-		 * There must be at least one regular lower layer
-		 * specified.
-		 */
-		if (ctx->nr == 0) {
-			pr_err("data lower layers without regular lower layers not allowed");
-			return -EINVAL;
-		}
-
-		/* Skip the leading "::". */
-		name += 2;
-		data_layer = true;
-		/*
-		 * A data layer is automatically an append as there
-		 * must've been at least one regular lower layer.
-		 */
-		append = true;
-	} else if (*name == ':') {
-		/*
-		 * This is a regular lower layer.
-		 * If users want to append a layer enforce that they
-		 * have already specified a first layer before. It's
-		 * better to be strict.
-		 */
-		if (ctx->nr == 0) {
-			pr_err("cannot append layer if no previous layer has been specified");
-			return -EINVAL;
-		}
-
-		/*
-		 * Once a sequence of data layers has started regular
-		 * lower layers are forbidden.
-		 */
-		if (ctx->nr_data > 0) {
-			pr_err("regular lower layers cannot follow data lower layers");
-			return -EINVAL;
-		}
-
-		/* Skip the leading ":". */
-		name++;
-		append = true;
+	if (*name == ':') {
+		pr_err("cannot append lower layer");
+		return -EINVAL;
 	}
 
 	dup = kstrdup(name, GFP_KERNEL);
@@ -472,7 +455,7 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 		l = &ctx->lower[nr];
 		memset(l, 0, sizeof(*l));
 
-		err = ovl_mount_dir_noesc(dup_iter, &l->path);
+		err = ovl_mount_dir(dup_iter, &l->path, false);
 		if (err)
 			goto out_put;
 
@@ -682,6 +665,7 @@ static int ovl_reconfigure(struct fs_context *fc)
 }
 
 static const struct fs_context_operations ovl_context_ops = {
+	.parse_monolithic = ovl_parse_monolithic,
 	.parse_param = ovl_parse_param,
 	.get_tree    = ovl_get_tree,
 	.reconfigure = ovl_reconfigure,
@@ -950,16 +934,23 @@ 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;
-	char **lowerdatadirs = &ofs->config.lowerdirs[nr_merged_lower];
-
-	/* lowerdirs[] starts from offset 1 */
-	seq_printf(m, ",lowerdir=%s", ofs->config.lowerdirs[1]);
-	/* dump regular lower layers */
-	for (nr = 2; nr < nr_merged_lower; nr++)
-		seq_printf(m, ":%s", ofs->config.lowerdirs[nr]);
-	/* dump data lower layers */
-	for (nr = 0; nr < ofs->numdatalayer; nr++)
-		seq_printf(m, "::%s", lowerdatadirs[nr]);
+
+	/*
+	 * 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.
+	 */
+	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 (ofs->config.upperdir) {
 		seq_show_option(m, "upperdir", ofs->config.upperdir);
 		seq_show_option(m, "workdir", ofs->config.workdir);