Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753733AbZK0XGG (ORCPT ); Fri, 27 Nov 2009 18:06:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753305AbZK0XGE (ORCPT ); Fri, 27 Nov 2009 18:06:04 -0500 Received: from server1.wserver.cz ([82.113.45.157]:60418 "EHLO server1.wserver.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753063AbZK0XGD (ORCPT ); Fri, 27 Nov 2009 18:06:03 -0500 From: Jiri Slaby To: jirislaby@gmail.com Cc: mingo@elte.hu, nhorman@tuxdriver.com, sfr@canb.auug.org.au, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, marcin.slusarz@gmail.com, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, torvalds@linux-foundation.org, oleg@redhat.com Subject: [PATCH v3 04/27] sys_setrlimit: make sure ->rlim_max never grows Date: Sat, 28 Nov 2009 00:05:44 +0100 Message-Id: <1259363167-9347-4-git-send-email-jslaby@suse.cz> X-Mailer: git-send-email 1.6.5.3 In-Reply-To: <1259363167-9347-1-git-send-email-jslaby@suse.cz> References: <1259363167-9347-1-git-send-email-jslaby@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2289 Lines: 71 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 71e4eb1..4377cb3 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1249,10 +1249,6 @@ 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; @@ -1270,11 +1266,16 @@ 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; /* @@ -1288,7 +1289,7 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim) update_rlimit_cpu(current, new_rlim.rlim_cur); out: - return 0; + return retval; } /* -- 1.6.5.3 -- 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/