Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933389Ab1CZALS (ORCPT ); Fri, 25 Mar 2011 20:11:18 -0400 Received: from kroah.org ([198.145.64.141]:35875 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933273Ab1CZAG2 (ORCPT ); Fri, 25 Mar 2011 20:06:28 -0400 X-Mailbox-Line: From gregkh@clark.kroah.org Fri Mar 25 17:04:57 2011 Message-Id: <20110326000457.609510480@clark.kroah.org> User-Agent: quilt/0.48-16.4 Date: Fri, 25 Mar 2011 17:03:49 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Julien Tinnes , Oleg Nesterov Subject: [17/35] Prevent rt_sigqueueinfo and rt_tgsigqueueinfo from spoofing the signal code In-Reply-To: <20110326000509.GA29736@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2578 Lines: 74 2.6.33-longterm review patch. If anyone has any objections, please let us 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 --- kernel/signal.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2406,9 +2406,13 @@ SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, 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. */ @@ -2422,9 +2426,13 @@ long do_rt_tgsigqueueinfo(pid_t tgid, pi 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/