From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergey Senozhatsky Subject: [PATCH] rcu_read_lock/unlock protect find_task_by_vpid call Date: Fri, 29 Oct 2010 15:55:50 +0300 Message-ID: <20101029125550.GA3932@swordfish.minsk.epam.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Andrew Morton , Ingo Molnar To: Alexander Viro Return-path: Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Commit 4221a9918e38b7494cee341dda7b7b4bb8c04bde "Add RCU check for find_task_by_vpid()" introduced rcu_lockdep_assert to find_task_by_pid_ns. Assertion failed in sys_ioprio_get. The patch is fixing assertion failure in ioprio_set as well. =================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- kernel/pid.c:419 invoked rcu_dereference_check() without protection! rcu_scheduler_active = 1, debug_locks = 0 1 lock held by iotop/4254: #0: (tasklist_lock){.?.?..}, at: [] sys_ioprio_get+0x22/0x2da stack backtrace: Pid: 4254, comm: iotop Not tainted Call Trace: [] lockdep_rcu_dereference+0xaa/0xb2 [] find_task_by_pid_ns+0x4f/0x68 [] find_task_by_vpid+0x1d/0x1f [] sys_ioprio_get+0x50/0x2da [] system_call_fastpath+0x16/0x1b Signed-off-by: Sergey Senozhatsky --- diff --git a/fs/ioprio.c b/fs/ioprio.c index 748cfb9..666343d 100644 --- a/fs/ioprio.c +++ b/fs/ioprio.c @@ -113,8 +113,11 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio) case IOPRIO_WHO_PROCESS: if (!who) p = current; - else + else { + rcu_read_lock(); p = find_task_by_vpid(who); + rcu_read_unlock(); + } if (p) ret = set_task_ioprio(p, ioprio); break; @@ -202,8 +205,11 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who) case IOPRIO_WHO_PROCESS: if (!who) p = current; - else + else { + rcu_read_lock(); p = find_task_by_vpid(who); + rcu_read_unlock(); + } if (p) ret = get_task_ioprio(p); break;