Messages in this thread | | | Subject | Re: [PATCH] procfs: make /proc style symlinks behave like "normal" symlinks | From | (Eric W. Biederman) | Date | Thu, 19 Nov 2009 09:07:16 -0800 |
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Nacked-by: "Eric W. Biederman" <ebiederm@xmission.com>
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
Jeff Layton <jlayton@redhat.com> 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.
> + 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; > +}
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