Check remount options and print warning if there is any unchangeable
option.
Signed-off-by: Chengguang Xu <cgxu519@xxxxxxx>
---
Changes since v4:
- Only print warning when detecting unchangeable options in remount.
- Add validation of option 'default_permissions'.
- Fix potential memleak in ovl_remount().
Changes since v3:
- Fix error prone macro helper.
- Make another new patch to only include code around.
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 | 76 ++++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 71 insertions(+), 5 deletions(-)
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 0293635a..5fa1e6e 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);
@@ -542,14 +547,75 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
return ovl_parse_redirect_mode(config);
}
+static bool ovl_opt_bool_neq(bool new, bool old, const char *name)
+{
+ if (new != old) {
+ pr_err("overlayfs: option \"%s\" cannot be %s on remount.\n",
+ name, new ? "enabled" : "disabled");
+ return true;
+ }
+ return false;
+}
+
+static bool ovl_opt_string_neq(const char *new, const char *old,
+ const char *name)
+{
+ if (new && (!old || strcmp(new, old))) {
+ pr_err("overlayfs: option \"%s\" cannot be changed on remount.\n",
+ name);
+ return true;
+ }
+ return false;
+}
+
+#define ovl_config_opt_neq(old, new, name, type) \
+ ovl_opt_##type##_neq((old)->name, (new)->name, #name)
+
+/*
+ * In current stage we only print warning message but not return error code
+ * when detecting the behavior of setting new value to unchangeable options.
+ */
static int ovl_remount(struct super_block *sb, int *flags, char *data)
{
struct ovl_fs *ofs = sb->s_fs_info;
+ struct ovl_config *oc = &ofs->config;
+ struct ovl_config *nc;
+ int err;
if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
return -EROFS;
- return 0;
+ nc = kzalloc(sizeof(struct ovl_config), GFP_KERNEL);
+ if (!nc)
+ return -ENOMEM;
+
+ nc->index = oc->index;
+ nc->nfs_export = oc->nfs_export;
+ nc->default_permissions = oc->default_permissions;
+
+ err = ovl_parse_opt((char *)data, nc);
+ if (err)
+ goto out_err;
+
+ if (ovl_config_opt_neq(nc, oc, index, bool))
+ goto out_err;
+ if (ovl_config_opt_neq(nc, oc, nfs_export, bool))
+ goto out_err;
+ if (ovl_config_opt_neq(nc, oc, default_permissions, bool))
+ goto out_err;
+ if (ovl_config_opt_neq(nc, oc, lowerdir, string))
+ goto out_err;
+ if (ovl_config_opt_neq(nc, oc, upperdir, string))
+ goto out_err;
+ if (ovl_config_opt_neq(nc, oc, workdir, string))
+ goto out_err;
+ if (ovl_config_opt_neq(nc, oc, redirect_mode, string))
+ goto out_err;
+
+out_err:
+ ovl_free_config(nc);
+ kfree(nc);
+ return err;
}
static const struct super_operations ovl_super_operations = {
--
1.8.3.1
--
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