Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753668Ab0FWVwx (ORCPT ); Wed, 23 Jun 2010 17:52:53 -0400 Received: from mail.pripojeni.net ([217.66.174.14]:37294 "EHLO mail.pripojeni.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1752024Ab0FWVwt (ORCPT ); Wed, 23 Jun 2010 17:52:49 -0400 From: Jiri Slaby To: jirislaby@gmail.com Cc: Oleg Nesterov , akpm@linux-foundation.org, adobriyan@gmail.com, nhorman@tuxdriver.com, Stephen Smalley , James Morris , Eric Paris , linux-kernel@vger.kernel.org Subject: [PATCH v4 03/12] rlimits: make sure ->rlim_max never grows in sys_setrlimit Date: Wed, 23 Jun 2010 23:52:04 +0200 Message-Id: <1277329933-8139-3-git-send-email-jslaby@suse.cz> X-Mailer: git-send-email 1.7.1 In-Reply-To: <1277329933-8139-1-git-send-email-jslaby@suse.cz> References: <1277329933-8139-1-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: 2280 Lines: 72 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 f5183b0..f2b2d7a 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1283,10 +1283,6 @@ 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; @@ -1304,11 +1300,16 @@ 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)) + retval = -EPERM; + else + *old_rlim = new_rlim; task_unlock(current->group_leader); - if (resource != RLIMIT_CPU) + if (retval || resource != RLIMIT_CPU) goto out; /* @@ -1322,7 +1323,7 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim) update_rlimit_cpu(current, new_rlim.rlim_cur); out: - return 0; + return retval; } /* -- 1.7.1 -- 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/