On Tue, Mar 21, 2017 at 7:51 AM, Omar Sandoval <osandov@xxxxxxxxxxx> wrote:
> */
> -int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry, struct inode **delegated_inode)
> +int vfs_link(struct dentry *old_dentry, struct inode *dir,
> + struct dentry *new_dentry, struct inode **delegated_inode,
> + unsigned int flags)
> {
> struct inode *inode = old_dentry->d_inode;
> + struct inode *target = new_dentry->d_inode;
> unsigned max_links = dir->i_sb->s_max_links;
> int error;
>
> if (!inode)
> return -ENOENT;
>
> - error = may_create(dir, new_dentry);
> + if (target) {
> + if (flags & AT_REPLACE)
> + error = may_delete(dir, new_dentry, d_is_dir(old_dentry));
> + else
> + error = -EEXIST;
> + } else {
> + error = may_create(dir, new_dentry);
> + }
This looks bogus.
In particular, that "may_delete()" cannot be right. It should still
*also* have the right to create something in that directory.
But even if you replace it with checks for both deletion _and_
creation, it won't be right, since the test for d_is_negative() on the
target in may_delete() looks wrong for this situation.
Normally, you cannot delete a negative entry (think of what that would
do in a overlay situation), but it should still be ok to link a
positive entry on top of a negative one.
Also, I think the above is incorrect for yet another case: moving
somethign on top of a directory should be disallowed. We do later on
check that the *source* isn't a directory (since you can't link
directories), but I'm not seeing where you'd be checking that you
don't move over a directory either.
So I don't think this patch is acceptable as such. I also suspect that
it should be done in multiple phases.
Linus
