tree f5ceb1dd84f1c19467fb619e0634f11e5976fecd
parent dc9c034c854e3a6e004062a84806a07af6008a34
author Gaurav Aggarwal <aggarg@amazon.com> 1659611493 +0530
committer Paul Bartell <paul.bartell@gmail.com> 1659632279 -0700

Fix NULL pointer dereference in vPortGetHeapStats

When the heap is exhausted (no free block), start and end markers are
the only blocks present in the free block list:

     +---------------+     +-----------> NULL
     |               |     |
     |               V     |
+ ----- +            + ----- +
|   |   |            |   |   |
|   |   |            |   |   |
+ ----- +            + ----- +
  xStart               pxEnd

The code block which traverses the list of free blocks to calculate heap
stats used a do..while loop that moved past the end marker when the heap
had no free block resulting in a NULL pointer dereference. This commit
changes the do..while loop to while loop thereby ensuring that we never
move past the end marker.

This was reported here - https://github.com/FreeRTOS/FreeRTOS-Kernel/issues/534

Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>