[PATCH 2/4] ipc/mqueue: switch back to using non-max values on create

[Doug Ledford <dledford@redhat.com>]

Commit b231cca4381ee15ec99afbfb244fbc0324869927 changed
how we create a queue that does not include an attr
struct passed to open so that it creates the queue
with whatever the maximum values are.  However, if the
admin has set the maximums to allow flexibility in
creating a queue (aka, both a large size and large queue
are allowed, but combined they create a queue too large
for the RLIMIT_MSGQUEUE of the user), then attempts to
create a queue without an attr struct will fail.  Switch
back to using acceptable defaults regardless of what
the maximums are.

Signed-off-by: Doug Ledford <dledford@redhat.com>
---
 include/linux/ipc_namespace.h |    2 ++
 ipc/mqueue.c                  |    5 +++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index 1372b56..bde094e 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -95,9 +95,11 @@ extern int mq_init_ns(struct ipc_namespace *ns);
 #define DFLT_QUEUESMAX 256     /* max number of message queues */
 #define HARD_QUEUESMAX 1024
 #define MIN_MSGMAX     1
+#define DFLT_MSG       10U
 #define DFLT_MSGMAX    10      /* max number of messages in each queue */
 #define HARD_MSGMAX    (32768*sizeof(void *)/4)
 #define MIN_MSGSIZEMAX  128
+#define DFLT_MSGSIZE    8192U
 #define DFLT_MSGSIZEMAX 8192   /* max message size */
 #define HARD_MSGSIZEMAX (8192*128)
 #else
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index ed049ea..c6597fc 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -142,8 +142,9 @@ static struct inode *mqueue_get_inode(struct super_block *sb,
 		info->qsize = 0;
 		info->user = NULL;	/* set when all is ok */
 		memset(&info->attr, 0, sizeof(info->attr));
-		info->attr.mq_maxmsg = ipc_ns->mq_msg_max;
-		info->attr.mq_msgsize = ipc_ns->mq_msgsize_max;
+		info->attr.mq_maxmsg = min(ipc_ns->mq_msg_max, DFLT_MSG);
+		info->attr.mq_msgsize =
+			min(ipc_ns->mq_msgsize_max, DFLT_MSGSIZE);
 		if (attr) {
 			info->attr.mq_maxmsg = attr->mq_maxmsg;
 			info->attr.mq_msgsize = attr->mq_msgsize;
-- 
1.7.6