Hi Miklos,
Looking at the following:
int ovl_copy_up(struct dentry *dentry)
{
int err;
err = 0;
while (!err) {
struct dentry *next;
struct dentry *parent;
struct path lowerpath;
struct kstat stat;
enum ovl_path_type type = ovl_path_type(dentry);
if (type != OVL_PATH_LOWER)
break;
next = dget(dentry);
/* find the topmost dentry not yet copied up */
for (;;) {
parent = dget_parent(next);
type = ovl_path_type(parent);
if (type != OVL_PATH_LOWER)
break;
dput(next);
next = parent;
}
ovl_path_lower(next, &lowerpath);
err = vfs_getattr(&lowerpath, &stat);
if (!err)
err = ovl_copy_up_one(parent, next, &lowerpath,
&stat);
dput(parent);
dput(next);
}
return err;
}
In the for-loop in the middle, if you ascend any levels at all, how are you
protected from racing with copy-ups taking place on those more rootwards
dentries?
I can see ovl_copy_up_one() using lock_rename() on the workdir and upperdir,
but there's no relevant lock on the overlayfs fs. You stepped out of the lock
the VFS caller holds when you ascended.
David
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