Check remount options and return error if there is any unchangeable
option.
Signed-off-by: Chengguang Xu <cgxu519@xxxxxxx>
---
Changes since v2:
- Introduce two macro helpers to simplify remount option validation.
Changes since v1:
- Refactor ovl_free_fs(), move config freeing operations to ovl_free_config()
fs/overlayfs/super.c | 103 ++++++++++++++++++++++++++++++++++++++-------------
1 file changed, 78 insertions(+), 25 deletions(-)
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index a2a7b7a..dd9f828 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -230,6 +230,14 @@ static void ovl_destroy_inode(struct inode *inode)
call_rcu(&inode->i_rcu, ovl_i_callback);
}
+static void ovl_free_config(struct ovl_config *config)
+{
+ kfree(config->lowerdir);
+ kfree(config->upperdir);
+ kfree(config->workdir);
+ kfree(config->redirect_mode);
+}
+
static void ovl_free_fs(struct ovl_fs *ofs)
{
unsigned i;
@@ -249,10 +257,7 @@ static void ovl_free_fs(struct ovl_fs *ofs)
kfree(ofs->lower_layers);
kfree(ofs->lower_fs);
- kfree(ofs->config.lowerdir);
- kfree(ofs->config.upperdir);
- kfree(ofs->config.workdir);
- kfree(ofs->config.redirect_mode);
+ ovl_free_config(&ofs->config);
if (ofs->creator_cred)
put_cred(ofs->creator_cred);
kfree(ofs);
@@ -379,27 +384,6 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
return 0;
}
-static int ovl_remount(struct super_block *sb, int *flags, char *data)
-{
- struct ovl_fs *ofs = sb->s_fs_info;
-
- if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
- return -EROFS;
-
- return 0;
-}
-
-static const struct super_operations ovl_super_operations = {
- .alloc_inode = ovl_alloc_inode,
- .destroy_inode = ovl_destroy_inode,
- .drop_inode = generic_delete_inode,
- .put_super = ovl_put_super,
- .sync_fs = ovl_sync_fs,
- .statfs = ovl_statfs,
- .show_options = ovl_show_options,
- .remount_fs = ovl_remount,
-};
-
enum {
OPT_LOWERDIR,
OPT_UPPERDIR,
@@ -563,6 +547,75 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
return ovl_parse_redirect_mode(config, config->redirect_mode);
}
+#define ovl_option_bool_neq(new, old, x, y, z) \
+do { \
+ if (new->x != old->x) { \
+ pr_err("overlayfs: option %s cannot be changed on remount.\n", y); \
+ goto z; \
+ } \
+} while (0)
+
+#define ovl_option_string_neq(new, old, x, y, z) \
+do { \
+ if (new->x && (!old->x || strcmp(new->x, old->x))) { \
+ pr_err("overlayfs: option %s cannot be changed on remount.\n", y); \
+ goto z; \
+ } \
+} while (0)
+
+static int ovl_remount(struct super_block *sb, int *flags, char *data)
+{
+ struct ovl_fs *ofs = sb->s_fs_info;
+ struct ovl_config *old_config = &ofs->config;
+ struct ovl_config *new_config;
+ int err;
+
+ if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
+ return -EROFS;
+
+ new_config = kzalloc(sizeof(struct ovl_config), GFP_KERNEL);
+ if (!new_config)
+ return -ENOMEM;
+
+ new_config->index = old_config->index;
+ new_config->nfs_export = old_config->nfs_export;
+
+ err = ovl_parse_opt((char *)data, new_config);
+ if (err)
+ goto out_err;
+
+ err = -EINVAL;
+ ovl_option_bool_neq(new_config, old_config, index,
+ "index", out_err);
+ ovl_option_bool_neq(new_config, old_config, nfs_export,
+ "nfs_export", out_err);
+ ovl_option_string_neq(new_config, old_config, lowerdir,
+ "lowerdir", out_err);
+ ovl_option_string_neq(new_config, old_config, upperdir,
+ "upperdir", out_err);
+ ovl_option_string_neq(new_config, old_config, workdir,
+ "workdir", out_err);
+ ovl_option_string_neq(new_config, old_config, redirect_mode,
+ "redirect_mode", out_err);
+ return 0;
+
+out_err:
+ ovl_free_config(new_config);
+ kfree(new_config);
+ return err;
+}
+
+static const struct super_operations ovl_super_operations = {
+ .alloc_inode = ovl_alloc_inode,
+ .destroy_inode = ovl_destroy_inode,
+ .drop_inode = generic_delete_inode,
+ .put_super = ovl_put_super,
+ .sync_fs = ovl_sync_fs,
+ .statfs = ovl_statfs,
+ .show_options = ovl_show_options,
+ .remount_fs = ovl_remount,
+};
+
#define OVL_WORKDIR_NAME "work"
#define OVL_INDEXDIR_NAME "index"
--
1.8.3.1
--
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