Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754160Ab1C1VZE (ORCPT ); Mon, 28 Mar 2011 17:25:04 -0400 Received: from smtp-out.google.com ([216.239.44.51]:63394 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751160Ab1C1VZB convert rfc822-to-8bit (ORCPT ); Mon, 28 Mar 2011 17:25:01 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=P2G1VrCf2zp/vEgRf08V2KrV4/NtForlmxh5CVpYuRICycvvvP2zP+3TrUIuUK5zC7 KL79hxN5V810/KXGMpUw== MIME-Version: 1.0 In-Reply-To: <1301346815-6755-1-git-send-email-roland@kernel.org> References: <1301346815-6755-1-git-send-email-roland@kernel.org> Date: Mon, 28 Mar 2011 14:24:57 -0700 Message-ID: Subject: Re: [PATCH v2] Relax si_code check in rt_sigqueueinfo and rt_tgsigqueueinfo From: Julien Tinnes To: Roland Dreier Cc: Linus Torvalds , linux-kernel@vger.kernel.org, Oleg Nesterov , Klaus Dittrich Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2716 Lines: 65 Ohh, good catch! It's not ideal that we have to relax this check, but as long as kernel codes, SI_USER and SI_TKILL are not spoofable, I think we're in ok shape. Thanks, Julien On Mon, Mar 28, 2011 at 2:13 PM, Roland Dreier wrote: > From: Roland Dreier > > Commit da48524eb206 ("Prevent rt_sigqueueinfo and rt_tgsigqueueinfo > from spoofing the signal code") made the check on si_code too strict. > There are several legitimate places where glibc wants to queue a > negative si_code different from SI_QUEUE: > > ?- This was first noticed with glibc's aio implementation, which wants > ? to queue a signal with si_code SI_ASYNCIO; the current kernel > ? causes glibc's tst-aio4 test to fail because rt_sigqueueinfo() > ? fails with EPERM. > > ?- Further examination of the glibc source shows that getaddrinfo_a() > ? wants to use SI_ASYNCNL (which the kernel does not even define). > ? The timer_create() fallback code wants to queue signals with SI_TIMER. > > As suggested by Oleg Nesterov , loosen the check to > forbid only the problematic SI_TKILL case. > > Reported-by: Klaus Dittrich > Cc: > Signed-off-by: Roland Dreier > --- > ?kernel/signal.c | ? ?4 ++-- > ?1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/signal.c b/kernel/signal.c > index 324eff5..b2bfa3a 100644 > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -2437,7 +2437,7 @@ SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig, > ? ? ? ?/* Not even root can pretend to send signals from the kernel. > ? ? ? ? * Nor can they impersonate a kill()/tgkill(), which adds source info. > ? ? ? ? */ > - ? ? ? if (info.si_code != SI_QUEUE) { > + ? ? ? if (info.si_code >= 0 || info.si_code == SI_TKILL) { > ? ? ? ? ? ? ? ?/* We used to allow any < 0 si_code */ > ? ? ? ? ? ? ? ?WARN_ON_ONCE(info.si_code < 0); > ? ? ? ? ? ? ? ?return -EPERM; > @@ -2457,7 +2457,7 @@ long do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, siginfo_t *info) > ? ? ? ?/* Not even root can pretend to send signals from the kernel. > ? ? ? ? * Nor can they impersonate a kill()/tgkill(), which adds source info. > ? ? ? ? */ > - ? ? ? if (info->si_code != SI_QUEUE) { > + ? ? ? if (info->si_code >= 0 || info->si_code == SI_TKILL) { > ? ? ? ? ? ? ? ?/* We used to allow any < 0 si_code */ > ? ? ? ? ? ? ? ?WARN_ON_ONCE(info->si_code < 0); > ? ? ? ? ? ? ? ?return -EPERM; > -- 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/