From: Eric Biggers Subject: Re: [PATCH] dh key: fix rounding up KDF output length Date: Mon, 25 Jun 2018 10:14:26 -0700 Message-ID: <20180625171426.GA180889@gmail.com> References: <20180607191201.97080-1-ebiggers3@gmail.com> <0000000000009c221d056e0cf53a@google.com> <17595.1528472278@warthog.procyon.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: James Morris , keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, Tycho Andersen , Kees Cook , Stephan Mueller , Eric Biggers To: David Howells Return-path: Content-Disposition: inline In-Reply-To: <17595.1528472278@warthog.procyon.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org Hi David, On Fri, Jun 08, 2018 at 04:37:58PM +0100, David Howells wrote: > Eric Biggers wrote: > > > Commit 383203eff718 ("dh key: get rid of stack allocated array") changed > > kdf_ctr() to assume that the length of key material to derive is a > > multiple of the digest size. The length was supposed to be rounded up > > accordingly. However, the round_up() macro was used which only gives > > the correct result on power-of-2 arguments, whereas not all hash > > algorithms have power-of-2 digest sizes. In some cases this resulted in > > a write past the end of the 'outbuf' buffer. > > > > Fix it by switching to roundup(), which works for non-power-of-2 inputs. > > Applied. Applied to where? When are you planning to send this to Linus? Note that this was a regression from v4.17 to v4.18-rc1. Thanks, - Eric