From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boaz Harrosh Subject: Re: Checking link targets are NULL-terminated Date: Tue, 09 Dec 2008 20:00:12 +0200 Message-ID: <493EB22C.2050108@panasas.com> References: <20081205144810.GA25585@dastardly.home.dghda.com> <20081208143003.9449bc77.akpm@linux-foundation.org> <20081209171814.GA8667@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Andrew Morton , Duane Griffin , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org To: Christoph Hellwig Return-path: In-Reply-To: <20081209171814.GA8667@infradead.org> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Christoph Hellwig wrote: > On Mon, Dec 08, 2008 at 02:30:03PM -0800, Andrew Morton wrote: >> Perhaps nd_set_link() is a suitable place? Change that function so >> that it is passed a third argument (max_len) and then check that within >> nd_set_link(). Change nd_set_link() to return a __must_check-marked >> errno, change callers to handle errors appropriately. >> >> Or something totally different ;) But along those lines? > > Note that XFS and possibly other filesystem don't store the NULL > termination on disk. Note that ext2, for example, also only writes the string bytes without any NULLs. It only happen to be zero padded because any last-page is zero-padded from i_size to end of page. > So having a follow_link interface that uses a > counted string would be a nice little optimization for the XFS > follow_link / readlink implementation. But I'm not really sure it's > worth complicating the VFS for that little gem. > The inode's i_size already holds the string count so at the higher level we have that information. But I'm convinced, nd_set_link() should receive a new max_len, all users should be changed as a matter of code audit. nd_set_link() should then proceed to truncate the string at that length unconditionally no need for error returns. My $0.017 Boaz