ipc: don't allocate a copy larger than max

When MSG_COPY is set, a duplicate message must be allocated for the copy
before locking the queue.  However, the copy could not be larger than was
sent which is limited to msg_ctlmax.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/ipc/msg.c b/ipc/msg.c
index 950572f..31cd1bf 100644 (file)
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -820,15 +820,17 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp,
        struct msg_msg *copy = NULL;
        unsigned long copy_number = 0;
 
+       ns = current->nsproxy->ipc_ns;
+
        if (msqid < 0 || (long) bufsz < 0)
                return -EINVAL;
        if (msgflg & MSG_COPY) {
-               copy = prepare_copy(buf, bufsz, msgflg, &msgtyp, &copy_number);
+               copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax),
+                                   msgflg, &msgtyp, &copy_number);
                if (IS_ERR(copy))
                        return PTR_ERR(copy);
        }
        mode = convert_mode(&msgtyp, msgflg);
-       ns = current->nsproxy->ipc_ns;
 
        msq = msg_lock_check(ns, msqid);
        if (IS_ERR(msq)) {