From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarkko Sakkinen Date: Fri, 20 Mar 2020 02:07:17 +0000 Subject: Re: [PATCH v5 2/2] KEYS: Avoid false positive ENOMEM error on key read Message-Id: <20200320020717.GC183331@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit List-Id: References: <20200318221457.1330-1-longman@redhat.com> <20200318221457.1330-3-longman@redhat.com> <20200319194650.GA24804@linux.intel.com> In-Reply-To: To: Waiman Long Cc: David Howells , James Morris , "Serge E. Hallyn" , Mimi Zohar , "David S. Miller" , Jakub Kicinski , keyrings@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org, netdev@vger.kernel.org, linux-afs@lists.infradead.org, Sumit Garg , Jerry Snitselaar , Roberto Sassu , Eric Biggers , Chris von Recklinghausen On Thu, Mar 19, 2020 at 08:07:55PM -0400, Waiman Long wrote: > On 3/19/20 3:46 PM, Jarkko Sakkinen wrote: > > On Wed, Mar 18, 2020 at 06:14:57PM -0400, Waiman Long wrote: > >> + * It is possible, though unlikely, that the key > >> + * changes in between the up_read->down_read period. > >> + * If the key becomes longer, we will have to > >> + * allocate a larger buffer and redo the key read > >> + * again. > >> + */ > >> + if (!tmpbuf || unlikely(ret > tmpbuflen)) { > > Shouldn't you check that tmpbuflen stays below buflen (why else > > you had made copy of buflen otherwise)? > > The check above this thunk: > > if ((ret > 0) && (ret <= buflen)) { > > will make sure that ret will not be larger than buflen. So tmpbuflen > will never be bigger than buflen. Ah right, of course, thanks. What would go wrong if the condition was instead ((ret > 0) && (ret <= tmpbuflen))? /Jarkko