From e3bbfa2d8515a9cf83e4f9daef30c522f25835bd Mon Sep 17 00:00:00 2001
From: Gregory Nutt <gnutt@nuttx.org>
Date: Thu, 15 Sep 2016 12:42:24 -0600
Subject: [PATCH] mq_send() was not setting the errno value on certain failures
 to allocate a message

---
 sched/mqueue/mq_send.c        | 16 ++++++++++++++--
 sched/mqueue/mq_sndinternal.c | 21 ++++++++++++++-------
 sched/mqueue/mq_timedsend.c   |  6 ++++--
 3 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/sched/mqueue/mq_send.c b/sched/mqueue/mq_send.c
index df1500e035..12ce2b85c1 100644
--- a/sched/mqueue/mq_send.c
+++ b/sched/mqueue/mq_send.c
@@ -133,6 +133,15 @@ int mq_send(mqd_t mqdes, FAR const char *msg, size_t msglen, int prio)
 
       leave_critical_section(flags);
       mqmsg = mq_msgalloc();
+
+      /* Check if the message was sucessfully allocated */
+
+      if (mqmsg == NULL)
+        {
+          /* No... mq_msgalloc() does not set the errno value */
+
+          set_errno(ENOMEM);
+        }
     }
   else
     {
@@ -141,6 +150,8 @@ int mq_send(mqd_t mqdes, FAR const char *msg, size_t msglen, int prio)
        * - We are not in an interrupt handler AND
        * - The message queue is full AND
        * - When we tried waiting, the wait was unsuccessful.
+       *
+       * In this case mq_waitsend() has already set the errno value.
        */
 
       leave_critical_section(flags);
@@ -151,9 +162,10 @@ int mq_send(mqd_t mqdes, FAR const char *msg, size_t msglen, int prio)
    * to allocate it) or because the allocation failed.
    */
 
-  if (mqmsg)
+  if (mqmsg != NULL)
     {
-      /* Yes, perform the message send.
+      /* The allocation was successful (implying that we can also send the
+       * message). Perform the message send.
        *
        * NOTE: There is a race condition here: What if a message is added by
        * interrupt related logic so that queue again becomes non-empty.
diff --git a/sched/mqueue/mq_sndinternal.c b/sched/mqueue/mq_sndinternal.c
index 050d71269a..087e1f15dc 100644
--- a/sched/mqueue/mq_sndinternal.c
+++ b/sched/mqueue/mq_sndinternal.c
@@ -158,7 +158,7 @@ FAR struct mqueue_msg_s *mq_msgalloc(void)
       /* Try the general free list */
 
       mqmsg = (FAR struct mqueue_msg_s *)sq_remfirst(&g_msgfree);
-      if (!mqmsg)
+      if (mqmsg == NULL)
         {
           /* Try the free list reserved for interrupt handlers */
 
@@ -178,16 +178,23 @@ FAR struct mqueue_msg_s *mq_msgalloc(void)
       mqmsg = (FAR struct mqueue_msg_s *)sq_remfirst(&g_msgfree);
       leave_critical_section(flags);
 
-      /* If we cannot a message from the free list, then we will have to allocate one. */
+      /* If we cannot a message from the free list, then we will have to
+       * allocate one.
+       */
 
-      if (!mqmsg)
+      if (mqmsg == NULL)
         {
-          mqmsg = (FAR struct mqueue_msg_s *)kmm_malloc((sizeof (struct mqueue_msg_s)));
+          mqmsg = (FAR struct mqueue_msg_s *)
+            kmm_malloc((sizeof (struct mqueue_msg_s)));
 
-          /* Check if we got an allocated message */
+          /* Check if we allocated the message */
 
-          ASSERT(mqmsg);
-          mqmsg->type = MQ_ALLOC_DYN;
+          if (mqmsg != NULL)
+            {
+              /* Yes... remember that this message was dynamically allocated */
+
+              mqmsg->type = MQ_ALLOC_DYN;
+            }
         }
     }
 
diff --git a/sched/mqueue/mq_timedsend.c b/sched/mqueue/mq_timedsend.c
index 860e6223db..ffece37b8c 100644
--- a/sched/mqueue/mq_timedsend.c
+++ b/sched/mqueue/mq_timedsend.c
@@ -192,9 +192,11 @@ int mq_timedsend(mqd_t mqdes, FAR const char *msg, size_t msglen, int prio,
   /* Pre-allocate a message structure */
 
   mqmsg = mq_msgalloc();
-  if (!mqmsg)
+  if (mqmsg == NULL)
     {
-      /* Failed to allocate the message */
+      /* Failed to allocate the message. mq_msgalloc() will have set the
+       * errno to ENOMEM.
+       */
 
       set_errno(ENOMEM);
       return ERROR;