ovl: upper fs should not be R/O
After importing multi-lower layer support, users could mount a r/o
partition as the left most lowerdir instead of using it as upperdir.
And a r/o upperdir may cause an error like
overlayfs: failed to create directory ./workdir/work
during mount.
This patch check the *s_flags* of upper fs and return an error if
it is a r/o partition. The checking of *upper_mnt->mnt_sb->s_flags*
can be removed now.
This patch also remove
/* FIXME: workdir is not needed for a R/O mount */
from ovl_fill_super() because:
1) for upper fs r/o case
Setting a r/o partition as upper is prevented, no need to care about
workdir in this case.
2) for "mount overlay -o ro" with a r/w upper fs case
Users could remount overlayfs to r/w in this case, so workdir should
not be omitted.
Signed-off-by: hujianyang <hujianyang@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index edbb3eb..5f0d199 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -529,8 +529,7 @@
{
struct ovl_fs *ufs = sb->s_fs_info;
- if (!(*flags & MS_RDONLY) &&
- (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY)))
+ if (!(*flags & MS_RDONLY) && !ufs->upper_mnt)
return -EROFS;
return 0;
@@ -619,6 +618,15 @@
return -EINVAL;
}
}
+
+ /* Workdir is useless in non-upper mount */
+ if (!config->upperdir && config->workdir) {
+ pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
+ config->workdir);
+ kfree(config->workdir);
+ config->workdir = NULL;
+ }
+
return 0;
}
@@ -838,7 +846,6 @@
sb->s_stack_depth = 0;
if (ufs->config.upperdir) {
- /* FIXME: workdir is not needed for a R/O mount */
if (!ufs->config.workdir) {
pr_err("overlayfs: missing 'workdir'\n");
goto out_free_config;
@@ -848,6 +855,13 @@
if (err)
goto out_free_config;
+ /* Upper fs should not be r/o */
+ if (upperpath.mnt->mnt_sb->s_flags & MS_RDONLY) {
+ pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
+ err = -EINVAL;
+ goto out_put_upperpath;
+ }
+
err = ovl_mount_dir(ufs->config.workdir, &workpath);
if (err)
goto out_put_upperpath;
@@ -939,8 +953,8 @@
ufs->numlower++;
}
- /* If the upper fs is r/o or nonexistent, we mark overlayfs r/o too */
- if (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY))
+ /* If the upper fs is nonexistent, we mark overlayfs r/o too */
+ if (!ufs->upper_mnt)
sb->s_flags |= MS_RDONLY;
sb->s_d_op = &ovl_dentry_operations;