From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH] net: core: scm: fix information leak to userland Date: Sat, 30 Oct 2010 16:33:25 +0200 Message-ID: <1288449205.2680.968.camel@edumazet-laptop> References: <1288448796-6147-1-git-send-email-segooon@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: kernel-janitors@vger.kernel.org, "David S. Miller" , "Eric W. Biederman" , Tejun Heo , "Serge E. Hallyn" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Vasiliy Kulikov Return-path: Received: from mail-wy0-f174.google.com ([74.125.82.174]:57807 "EHLO mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753702Ab0J3Odj (ORCPT ); Sat, 30 Oct 2010 10:33:39 -0400 In-Reply-To: <1288448796-6147-1-git-send-email-segooon@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: Le samedi 30 octobre 2010 =C3=A0 18:26 +0400, Vasiliy Kulikov a =C3=A9c= rit : > Structure cmsghdr is copied to userland with padding bytes > unitialized on architectures where __kernel_size_t is unsigned long. > It leads to leaking of contents of kernel stack memory. >=20 > Signed-off-by: Vasiliy Kulikov > --- > Compile tested. >=20 > net/core/scm.c | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) >=20 > diff --git a/net/core/scm.c b/net/core/scm.c > index 413cab8..a4a9b70 100644 > --- a/net/core/scm.c > +++ b/net/core/scm.c > @@ -233,6 +233,7 @@ int put_cmsg(struct msghdr * msg, int level, int = type, int len, void *data) > msg->msg_flags |=3D MSG_CTRUNC; > cmlen =3D msg->msg_controllen; > } > + memset(&cmhdr, 0, sizeof(cmhdr)); > cmhdr.cmsg_level =3D level; > cmhdr.cmsg_type =3D type; > cmhdr.cmsg_len =3D cmlen; ??? struct cmsghdr { __kernel_size_t cmsg_len; /* data byte count, including h= dr */ int cmsg_level; /* originating protocol */ int cmsg_type; /* protocol-specific type */ }; Could you explain where are the padding bytes ?