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Fix NULL pointer dereference in vPortGetHeapStats

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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>
This commit is contained in:
Gaurav Aggarwal 2022-08-04 16:41:33 +05:30 committed by Paul Bartell
parent dc9c034c85
commit 618e165fa7
2 changed files with 4 additions and 4 deletions
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4
portable/MemMang/heap_4.c
View File

@ -494,7 +494,7 @@ void vPortGetHeapStats( HeapStats_t * pxHeapStats )
* is initialised automatically when the first allocation is made. */ * is initialised automatically when the first allocation is made. */
if( pxBlock != NULL ) if( pxBlock != NULL )
{ {
do while( pxBlock != pxEnd )
{ {
/* Increment the number of blocks and record the largest block seen /* Increment the number of blocks and record the largest block seen
* so far. */ * so far. */
@ -513,7 +513,7 @@ void vPortGetHeapStats( HeapStats_t * pxHeapStats )
/* Move to the next block in the chain until the last block is /* Move to the next block in the chain until the last block is
* reached. */ * reached. */
pxBlock = pxBlock->pxNextFreeBlock; pxBlock = pxBlock->pxNextFreeBlock;
} while( pxBlock != pxEnd ); }
} }
} }
( void ) xTaskResumeAll(); ( void ) xTaskResumeAll();

4
portable/MemMang/heap_5.c
View File

@ -544,7 +544,7 @@ void vPortGetHeapStats( HeapStats_t * pxHeapStats )
* is initialised automatically when the first allocation is made. */ * is initialised automatically when the first allocation is made. */
if( pxBlock != NULL ) if( pxBlock != NULL )
{ {
do while( pxBlock != pxEnd )
{ {
/* Increment the number of blocks and record the largest block seen /* Increment the number of blocks and record the largest block seen
* so far. */ * so far. */
@ -569,7 +569,7 @@ void vPortGetHeapStats( HeapStats_t * pxHeapStats )
/* Move to the next block in the chain until the last block is /* Move to the next block in the chain until the last block is
* reached. */ * reached. */
pxBlock = pxBlock->pxNextFreeBlock; pxBlock = pxBlock->pxNextFreeBlock;
} while( pxBlock != pxEnd ); }
} }
} }
( void ) xTaskResumeAll(); ( void ) xTaskResumeAll();