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>

1 files changed, 4 insertions, 2 deletions

diff --git a/ipc/msg.c b/ipc/msg.c
index 950572f9d796..31cd1bf6af27 100644
--- 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)) {