Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965210Ab1C3VWM (ORCPT ); Wed, 30 Mar 2011 17:22:12 -0400 Received: from mga09.intel.com ([134.134.136.24]:9067 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964903Ab1C3VJd (ORCPT ); Wed, 30 Mar 2011 17:09:33 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.63,270,1299484800"; d="scan'208";a="727133915" From: Andi Kleen References: <20110330203.501921634@firstfloor.org> In-Reply-To: <20110330203.501921634@firstfloor.org> To: jln@google.com, oleg@redhat.com, torvalds@linux-foundation.org, gregkh@suse.de, ak@linux.intel.com, linux-kernel@vger.kernel.org, stable@kernel.org, tim.bird@am.sony.com Subject: [PATCH] [226/275] Prevent rt_sigqueueinfo and rt_tgsigqueueinfo from spoofing the signal code Message-Id: <20110330210751.A9ADB3E1A05@tassilo.jf.intel.com> Date: Wed, 30 Mar 2011 14:07:51 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2750 Lines: 74 2.6.35-longterm review patch. If anyone has any objections, please let me know. ------------------ From: Julien Tinnes commit da48524eb20662618854bb3df2db01fc65f3070c upstream. Userland should be able to trust the pid and uid of the sender of a signal if the si_code is SI_TKILL. Unfortunately, the kernel has historically allowed sigqueueinfo() to send any si_code at all (as long as it was negative - to distinguish it from kernel-generated signals like SIGILL etc), so it could spoof a SI_TKILL with incorrect siginfo values. Happily, it looks like glibc has always set si_code to the appropriate SI_QUEUE, so there are probably no actual user code that ever uses anything but the appropriate SI_QUEUE flag. So just tighten the check for si_code (we used to allow any negative value), and add a (one-time) warning in case there are binaries out there that might depend on using other si_code values. Signed-off-by: Julien Tinnes Acked-by: Oleg Nesterov Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman Signed-off-by: Andi Kleen --- kernel/signal.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) Index: linux-2.6.35.y/kernel/signal.c =================================================================== --- linux-2.6.35.y.orig/kernel/signal.c 2011-03-29 22:50:25.616602954 -0700 +++ linux-2.6.35.y/kernel/signal.c 2011-03-29 23:03:02.941224912 -0700 @@ -2410,9 +2410,13 @@ return -EFAULT; /* Not even root can pretend to send signals from the kernel. - Nor can they impersonate a kill(), which adds source info. */ - if (info.si_code >= 0) + * Nor can they impersonate a kill()/tgkill(), which adds source info. + */ + if (info.si_code != SI_QUEUE) { + /* We used to allow any < 0 si_code */ + WARN_ON_ONCE(info.si_code < 0); return -EPERM; + } info.si_signo = sig; /* POSIX.1b doesn't mention process groups. */ @@ -2426,9 +2430,13 @@ return -EINVAL; /* Not even root can pretend to send signals from the kernel. - Nor can they impersonate a kill(), which adds source info. */ - if (info->si_code >= 0) + * Nor can they impersonate a kill()/tgkill(), which adds source info. + */ + if (info->si_code != SI_QUEUE) { + /* We used to allow any < 0 si_code */ + WARN_ON_ONCE(info->si_code < 0); return -EPERM; + } info->si_signo = sig; return do_send_specific(tgid, pid, sig, info); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/