[ 058/100] ipc: dont allocate a copy larger than max

[Greg Kroah-Hartman]

3.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Hurley <pe...@hurleysoftware.com>

commit 88b9e456b1649722673ffa147914299799dc9041 upstream.

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 <pe...@hurleysoftware.com>
Acked-by: Stanislav Kinsbursky <skinsbur...@parallels.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 ipc/msg.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -820,15 +820,17 @@ long do_msgrcv(int msqid, void __user *b
        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)) {


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