From: Tycho Andersen Subject: Re: [PATCH] dh key: fix rounding up KDF output length Date: Thu, 7 Jun 2018 14:28:31 -0600 Message-ID: <20180607202831.GG9999@cisco> References: <0000000000009c221d056e0cf53a@google.com> <20180607191201.97080-1-ebiggers3@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Howells , 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, Kees Cook , Stephan Mueller , Eric Biggers To: Eric Biggers Return-path: Content-Disposition: inline In-Reply-To: <20180607191201.97080-1-ebiggers3@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org On Thu, Jun 07, 2018 at 12:12:01PM -0700, Eric Biggers wrote: > From: Eric Biggers > > 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. > > Reported-by: syzbot+486f97f892efeb2075a3@syzkaller.appspotmail.com > Reported-by: syzbot+29d17b7898b41ee120a5@syzkaller.appspotmail.com > Reported-by: syzbot+8a608baf8751184ec727@syzkaller.appspotmail.com > Reported-by: syzbot+d04e58bd384f1fe0b112@syzkaller.appspotmail.com > Fixes: 383203eff718 ("dh key: get rid of stack allocated array") > Signed-off-by: Eric Biggers Arg, thanks. Acked-by: Tycho Andersen