Re: [PATCH v10 4/5] io_uring: add fsetxattr and setxattr support

[Al Viro <viro@zeniv.linux.org.uk>]

On Thu, Dec 30, 2021 at 02:17:23AM +0000, Al Viro wrote:

> > +static int io_setxattr_prep(struct io_kiocb *req,
> > +			const struct io_uring_sqe *sqe)
> > +{
> > +	struct io_xattr *ix = &req->xattr;
> > +	const char __user *path;
> > +	int ret;
> > +
> > +	ret = __io_setxattr_prep(req, sqe);
> > +	if (ret)
> > +		return ret;
> > +
> > +	path = u64_to_user_ptr(READ_ONCE(sqe->addr3));
> > +
> > +	ix->filename = getname_flags(path, LOOKUP_FOLLOW, NULL);
> > +	if (IS_ERR(ix->filename)) {
> > +		ret = PTR_ERR(ix->filename);
> > +		ix->filename = NULL;
> > +	}
> > +
> > +	return ret;
> > +}
> 
> ... and here you use it and bring the pathname in.  Should the latter
> step fail, you restore ->filename to NULL and return an error.
> 
> Could you explain what kind of magic could allow the caller to tell
> whether ix->ctx.kname needs to be freed on error?  I don't see any way
> that could possibly work...

getxattr side has the same problem, AFAICS...