From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752200AbbJLPeE (ORCPT ); Mon, 12 Oct 2015 11:34:04 -0400 Received: from mail-wi0-f177.google.com ([209.85.212.177]:37968 "EHLO mail-wi0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751041AbbJLPeC (ORCPT ); Mon, 12 Oct 2015 11:34:02 -0400 From: "Amanieu d'Antras" To: linux-kernel@vger.kernel.org Cc: Oleg Nesterov , Andrew Morton , "Paul E. McKenney" , "Amanieu d'Antras" Subject: [PATCH] signal: Make the si_code check in rt_[tg]sigqueueinfo stricter Date: Mon, 12 Oct 2015 16:33:54 +0100 Message-Id: <1444664034-22446-1-git-send-email-amanieu@gmail.com> X-Mailer: git-send-email 2.6.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org rt_sigqueueinfo and rt_tgsigqueueinfo check the value of si_code to prevent a process from spoofing a kernel-generated signal or one generated by kill/tgkill. Unfortunately this check failed to take into account the fact that the si_code value seen by a user process is only the low 16 bits of the value in the kernel. It was still possible to spoof any si_code by ORing 0xffff into the top 16 bits. The check is tightened by checking the value of si_code that will be seen by a user program instead of the one in the kernel. Signed-off-by: Amanieu d'Antras --- kernel/signal.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/signal.c b/kernel/signal.c index 0f6bbbe..f3d4f39 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2989,7 +2989,7 @@ static int do_rt_sigqueueinfo(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 >= 0 || info->si_code == SI_TKILL) && + if (((short)info->si_code >= 0 || (short)info->si_code == SI_TKILL) && (task_pid_vnr(current) != pid)) return -EPERM; @@ -3037,7 +3037,7 @@ static int 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 >= 0 || info->si_code == SI_TKILL) && + if (((short)info->si_code >= 0 || (short)info->si_code == SI_TKILL) && (task_pid_vnr(current) != pid)) return -EPERM; -- 2.6.1