From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755407AbZICNwY (ORCPT ); Thu, 3 Sep 2009 09:52:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755345AbZICNwX (ORCPT ); Thu, 3 Sep 2009 09:52:23 -0400 Received: from server1.wserver.cz ([82.113.45.157]:43976 "EHLO server1.wserver.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755315AbZICNwW (ORCPT ); Thu, 3 Sep 2009 09:52:22 -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] core: allow setrlimit to non-current tasks Date: Thu, 3 Sep 2009 15:52:28 +0200 Message-Id: <1251985948-28965-1-git-send-email-jirislaby@gmail.com> X-Mailer: git-send-email 1.6.3.3 In-Reply-To: <4A9FC8DA.4090001@gmail.com> References: <4A9FC8DA.4090001@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Just for clarity. The current patch looks like this: -- Add locking to allow setrlimit accept task parameter other than current. Namely, lock tasklist_lock for read and check whether the task structure has sighand non-null. Do all the signal processing under that lock still held. We do this only for non-current tasks. Signed-off-by: Jiri Slaby Cc: Oleg Nesterov --- kernel/sys.c | 24 ++++++++++++++++++++---- 1 files changed, 20 insertions(+), 4 deletions(-) diff --git a/kernel/sys.c b/kernel/sys.c index ed500c8..85d5d4d 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1240,6 +1240,7 @@ int setrlimit(struct task_struct *tsk, unsigned int resource, struct rlimit *new_rlim) { struct rlimit *old_rlim; + unsigned int needs_locking = !same_thread_group(tsk, current); int retval; if (new_rlim->rlim_cur > new_rlim->rlim_max) @@ -1247,13 +1248,24 @@ int setrlimit(struct task_struct *tsk, unsigned int resource, if (resource == RLIMIT_NOFILE && new_rlim->rlim_max > sysctl_nr_open) return -EPERM; + /* optimization: 'current' doesn't need locking, e.g. setrlimit */ + if (needs_locking) { + /* protect tsk->signal and tsk->sighand from disappearing */ + read_lock(&tasklist_lock); + if (!tsk->sighand) { + retval = -ESRCH; + goto unlock; + } + } old_rlim = tsk->signal->rlim + resource; if ((new_rlim->rlim_max > old_rlim->rlim_max) && - !capable(CAP_SYS_RESOURCE)) - return -EPERM; + !capable(CAP_SYS_RESOURCE)) { + retval = -EPERM; + goto unlock; + } retval = security_task_setrlimit(tsk, resource, new_rlim); if (retval) - return retval; + goto unlock; if (resource == RLIMIT_CPU && new_rlim->rlim_cur == 0) { /* @@ -1283,7 +1295,11 @@ int setrlimit(struct task_struct *tsk, unsigned int resource, update_rlimit_cpu(tsk, new_rlim->rlim_cur); out: - return 0; + retval = 0; +unlock: + if (needs_locking) + read_unlock(&tasklist_lock); + return retval; } SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim) -- 1.6.3.3