fix(ipc): check overflow before modifying IPC state in send functions

_rt_mb_send_wait, _rt_mq_send_wait, and rt_mq_urgent modified mailbox
and message queue data structures before checking overflow conditions.
On overflow, they returned errors without rolling back changes, causing
state corruption. Moved overflow checks before state modifications so
the data structures stay consistent on the error path.

Signed-off-by: Srikanth Patchava <srpatcha@users.noreply.github.com>

Author: srpatcha

src/ipc.c

@@ -2661,23 +2661,21 @@ static rt_err_t _rt_mb_send_wait(rt_mailbox_t mb,
         }
     }
 
+    if(mb->entry >= RT_MB_ENTRY_MAX)
+    {
+        rt_spin_unlock_irqrestore(&(mb->spinlock), level);
+        return -RT_EFULL; /* value overflowed */
+    }
+
     /* set ptr */
     mb->msg_pool[mb->in_offset] = value;
     /* increase input offset */
     ++ mb->in_offset;
     if (mb->in_offset >= mb->size)
         mb->in_offset = 0;
 
-    if(mb->entry < RT_MB_ENTRY_MAX)
-    {
-        /* increase message entry */
-        mb->entry ++;
-    }
-    else
-    {
-        rt_spin_unlock_irqrestore(&(mb->spinlock), level);
-        return -RT_EFULL; /* value overflowed */
-    }
+    /* increase message entry */
+    mb->entry ++;
 
     /* resume suspended thread */
     if (!rt_list_isempty(&mb->parent.suspend_thread))
@@ -3503,6 +3501,16 @@ static rt_err_t _rt_mq_send_wait(rt_mq_t mq,
 
     /* disable interrupt */
     level = rt_spin_lock_irqsave(&(mq->spinlock));
+
+    if(mq->entry >= RT_MQ_ENTRY_MAX)
+    {
+        /* return message to free list */
+        msg->next = (struct rt_mq_message *)mq->msg_queue_free;
+        mq->msg_queue_free = msg;
+        rt_spin_unlock_irqrestore(&(mq->spinlock), level);
+        return -RT_EFULL; /* value overflowed */
+    }
+
 #ifdef RT_USING_MESSAGEQUEUE_PRIORITY
     msg->prio = prio;
     if (mq->msg_queue_head == RT_NULL)
@@ -3544,16 +3552,8 @@ static rt_err_t _rt_mq_send_wait(rt_mq_t mq,
         mq->msg_queue_head = msg;
 #endif
 
-    if(mq->entry < RT_MQ_ENTRY_MAX)
-    {
-        /* increase message entry */
-        mq->entry ++;
-    }
-    else
-    {
-        rt_spin_unlock_irqrestore(&(mq->spinlock), level);
-        return -RT_EFULL; /* value overflowed */
-    }
+    /* increase message entry */
+    mq->entry ++;
 
     /* resume suspended thread */
     if (!rt_list_isempty(&mq->parent.suspend_thread))
@@ -3694,6 +3694,15 @@ rt_err_t rt_mq_urgent(rt_mq_t mq, const void *buffer, rt_size_t size)
 
     level = rt_spin_lock_irqsave(&(mq->spinlock));
 
+    if(mq->entry >= RT_MQ_ENTRY_MAX)
+    {
+        /* return message to free list */
+        msg->next = (struct rt_mq_message *)mq->msg_queue_free;
+        mq->msg_queue_free = msg;
+        rt_spin_unlock_irqrestore(&(mq->spinlock), level);
+        return -RT_EFULL; /* value overflowed */
+    }
+
     /* link msg to the beginning of message queue */
     msg->next = (struct rt_mq_message *)mq->msg_queue_head;
     mq->msg_queue_head = msg;
@@ -3702,16 +3711,8 @@ rt_err_t rt_mq_urgent(rt_mq_t mq, const void *buffer, rt_size_t size)
     if (mq->msg_queue_tail == RT_NULL)
         mq->msg_queue_tail = msg;
 
-    if(mq->entry < RT_MQ_ENTRY_MAX)
-    {
-        /* increase message entry */
-        mq->entry ++;
-    }
-    else
-    {
-        rt_spin_unlock_irqrestore(&(mq->spinlock), level);
-        return -RT_EFULL; /* value overflowed */
-    }
+    /* increase message entry */
+    mq->entry ++;
 
     /* resume suspended thread */
     if (!rt_list_isempty(&mq->parent.suspend_thread))