From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756328AbZICUIk (ORCPT ); Thu, 3 Sep 2009 16:08:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756317AbZICUIj (ORCPT ); Thu, 3 Sep 2009 16:08:39 -0400 Received: from server1.wserver.cz ([82.113.45.157]:51030 "EHLO server1.wserver.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756273AbZICUIi (ORCPT ); Thu, 3 Sep 2009 16:08:38 -0400 From: Jiri Slaby To: oleg@redhat.com Cc: akpm@linux-foundation.org, mingo@redhat.com, linux-kernel@vger.kernel.org, Jiri Slaby Subject: [PATCH v2 4/8] sys_setrlimit: make sure ->rlim_max never grows Date: Thu, 3 Sep 2009 22:08:40 +0200 Message-Id: <1252008524-5376-4-git-send-email-jirislaby@gmail.com> X-Mailer: git-send-email 1.6.3.3 In-Reply-To: <20090903174106.GC27161@redhat.com> References: <20090903174106.GC27161@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Oleg Nesterov Mostly preparation for Jiri's changes, but probably makes sense anyway. sys_setrlimit() checks new_rlim.rlim_max <= old_rlim->rlim_max, but when it takes task_lock() old_rlim->rlim_max can be already lowered. Move this check under task_lock(). Currently this is not important, we can only race with our sub-thread, this means the application is stupid. But when we change the code to allow the update of !current task's limits, it becomes important to make sure ->rlim_max can be lowered "reliably" even if we race with the application doing sys_setrlimit(). Signed-off-by: Oleg Nesterov Signed-off-by: Jiri Slaby --- kernel/sys.c | 15 ++++++++------- 1 files changed, 8 insertions(+), 7 deletions(-) diff --git a/kernel/sys.c b/kernel/sys.c index d501f60..600d3e2 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1247,10 +1247,6 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim) return -EFAULT; if (new_rlim.rlim_cur > new_rlim.rlim_max) return -EINVAL; - old_rlim = current->signal->rlim + resource; - if ((new_rlim.rlim_max > old_rlim->rlim_max) && - !capable(CAP_SYS_RESOURCE)) - return -EPERM; if (resource == RLIMIT_NOFILE && new_rlim.rlim_max > sysctl_nr_open) return -EPERM; @@ -1268,11 +1264,16 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim) new_rlim.rlim_cur = 1; } + old_rlim = current->signal->rlim + resource; task_lock(current->group_leader); - *old_rlim = new_rlim; + if ((new_rlim.rlim_max <= old_rlim->rlim_max) || + capable(CAP_SYS_RESOURCE)) + *old_rlim = new_rlim; + else + retval = -EPERM; task_unlock(current->group_leader); - if (resource != RLIMIT_CPU) + if (retval || resource != RLIMIT_CPU) goto out; /* @@ -1286,7 +1287,7 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim) update_rlimit_cpu(current, new_rlim.rlim_cur); out: - return 0; + return retval; } /* -- 1.6.3.3