On Thu, 19 Nov 2009 09:07:16 -0800
ebiederm@xxxxxxxxxxxx (Eric W. Biederman) wrote:
>
> Nacked-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
>
> This is broken. If the referenced file is in a different mount namespace
> the path returned could point to a completely different path in your
> own mount namespace. Even in your own mount namespace this makes the
> proc symlinks racy and not guaranteed to return the file of interest.
>
> I don't see any hope of this approach ever working.
>
> Eric
>
Then is proc_pid_readlink broken in the same way?
>
> Jeff Layton <jlayton@xxxxxxxxxx> writes:
>
> > -static int proc_pid_readlink(struct dentry * dentry, char __user * buffer, int buflen)
> > -{
> > - int error = -EACCES;
> > - struct inode *inode = dentry->d_inode;
> > + struct page *page = NULL;
> > struct path path;
> > + int error;
> >
> > /* Are we allowed to snoop on the tasks file descriptors? */
> > - if (!proc_fd_access_allowed(inode))
> > + if (!proc_fd_access_allowed(inode)) {
> > + pathname = ERR_PTR(-EACCES);
> > goto out;
> > + }
> >
> > error = PROC_I(inode)->op.proc_get_link(inode, &path);
> > - if (error)
> > + if (error) {
> > + pathname = ERR_PTR(error);
> > goto out;
> > + }
> > +
> > + page = alloc_page(GFP_HIGHUSER);
> > + if (!page) {
> > + pathname = ERR_PTR(-ENOMEM);
> > + goto out_path_put;
> > + }
> > +
> > + pathname = kmap(page);
> > + pathname = d_path(&path, pathname, PAGE_SIZE);
>
> This is just nonsense.
>
How so? Care to elaborate?
>
> > + if (IS_ERR(pathname)) {
> > + kunmap(page);
> > + __free_page(page);
> > + page = NULL;
> > + }
> >
> > - error = do_proc_readlink(&path, buffer, buflen);
> > +out_path_put:
> > path_put(&path);
> > out:
> > - return error;
> > + nd_set_link(nd, pathname);
> > + return page;
> > +}
--
Jeff Layton <jlayton@xxxxxxxxxx>
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
