[PATCH] SUSv2 msgctl compliance

[Christopher Yeoh]

For msgctl SUSv2 states:

"IPC_SET can only be executed by a process with appropriate privileges
or that has an effective user ID equal to the value of msg_perm.cuid
or msg_perm.uid in the msqid_ds data structure associated with
msqid. Only a process with appropriate privileges can raise the value
of msg_qbytes."

The current linux behaviour is to allow for the value of msg_qbytes to
be raised even if the process is not privileged. The following
patch (against 2.4.19pre8) fixes this problem:

--- ipc/msg.c.orig	Fri May 24 14:51:12 2002
+++ ipc/msg.c	Fri May 24 14:58:36 2002
@@ -539,7 +539,8 @@
 	switch (cmd) {
 	case IPC_SET:
 	{
-		if (setbuf.qbytes > msg_ctlmnb && !capable(CAP_SYS_RESOURCE))
+		if (setbuf.qbytes > min(msg_ctlmnb, msq->q_qbytes) &&
+                    !capable(CAP_SYS_RESOURCE))
 			goto out_unlock_up;
 		msq->q_qbytes = setbuf.qbytes;
 
Chris
-- 
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IBM OzLabs Linux Development Group
Canberra, Australia