Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932383Ab3IPDFJ (ORCPT ); Sun, 15 Sep 2013 23:05:09 -0400 Received: from g1t0029.austin.hp.com ([15.216.28.36]:10966 "EHLO g1t0029.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932258Ab3IPDE5 (ORCPT ); Sun, 15 Sep 2013 23:04:57 -0400 From: Davidlohr Bueso To: Manfred Spraul , Linus Torvalds , Andrew Morton Cc: Rik van Riel , Mike Galbraith , sedat.dilek@gmail.com, Linux Kernel Mailing List , Davidlohr Bueso , stable@vger.kernel.org, #@domain.invalid, for@domain.invalid, 3.11@domain.invalid Subject: [PATCH 4/4] ipc,msg: prevent race with rmid in msgsnd,msgrcv Date: Sun, 15 Sep 2013 20:04:37 -0700 Message-Id: <1379300677-24188-5-git-send-email-davidlohr@hp.com> X-Mailer: git-send-email 1.7.11.7 In-Reply-To: <1379300677-24188-1-git-send-email-davidlohr@hp.com> References: <1379300677-24188-1-git-send-email-davidlohr@hp.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1879 Lines: 63 This fixes a race in both msgrcv() and msgsnd() between finding the msg and actually dealing with the queue, as another thread can delete shmid underneath us if we are preempted before acquiring the kern_ipc_perm.lock. Manfred illustrates this nicely: Assume a preemptible kernel that is preempted just after > msq = msq_obtain_object_check(ns, msqid) in do_msgrcv(). The only lock that is held is rcu_read_lock(). Now the other thread processes IPC_RMID. When the first task is resumed, then it will happily wait for messages on a deleted queue. Fix this by checking for if the queue has been deleted after taking the lock. Reported-by: Manfred Spraul Cc: stable@vger.kernel.org # for 3.11 Signed-off-by: Davidlohr Bueso --- ipc/msg.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/ipc/msg.c b/ipc/msg.c index 06e8aae..4e7d95a 100644 --- a/ipc/msg.c +++ b/ipc/msg.c @@ -690,6 +690,12 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext, if (ipcperms(ns, &msq->q_perm, S_IWUGO)) goto out_unlock0; + /* raced with RMID? */ + if (msq->q_perm.deleted) { + err = -EIDRM; + goto out_unlock0; + } + err = security_msg_queue_msgsnd(msq, msg, msgflg); if (err) goto out_unlock0; @@ -896,6 +902,13 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgfl goto out_unlock1; ipc_lock_object(&msq->q_perm); + + /* raced with RMID? */ + if (msq->q_perm.deleted) { + msg = ERR_PTR(-EIDRM); + goto out_unlock0; + } + msg = find_msg(msq, &msgtyp, mode); if (!IS_ERR(msg)) { /* -- 1.7.11.7 -- 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/