Subject: + ipcmsg-prevent-race-with-rmid-in-msgsndmsgrcv.patch added to -mm tree
To: davidlohr@xxxxxx,efault@xxxxxx,manfred@xxxxxxxxxxxxxxxx,riel@xxxxxxxxxx,stable@xxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Thu, 26 Sep 2013 23:05:18 -0700
The patch titled
Subject: ipc,msg: prevent race with rmid in msgsnd,msgrcv
has been added to the -mm tree. Its filename is
ipcmsg-prevent-race-with-rmid-in-msgsndmsgrcv.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ipcmsg-prevent-race-with-rmid-in-msgsndmsgrcv.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ipcmsg-prevent-race-with-rmid-in-msgsndmsgrcv.patch
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------------------------------------------------------
From: Davidlohr Bueso <davidlohr@xxxxxx>
Subject: ipc,msg: prevent race with rmid in msgsnd,msgrcv
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.
Signed-off-by: Davidlohr Bueso <davidlohr@xxxxxx>
Reported-by: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [3.11]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
ipc/msg.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff -puN ipc/msg.c~ipcmsg-prevent-race-with-rmid-in-msgsndmsgrcv ipc/msg.c
--- a/ipc/msg.c~ipcmsg-prevent-race-with-rmid-in-msgsndmsgrcv
+++ a/ipc/msg.c
@@ -695,6 +695,12 @@ long do_msgsnd(int msqid, long mtype, vo
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;
@@ -901,6 +907,13 @@ long do_msgrcv(int msqid, void __user *b
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)) {
/*
_
Patches currently in -mm which might be from davidlohr@xxxxxx are
origin.patch
ipc-semc-optimize-sem_lock.patch
ipcmsg-prevent-race-with-rmid-in-msgsndmsgrcv.patch
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