[dpdk-dev] [PATCH v3] mem: fix malloc_elem resize with padding

[Jamie Lavigne <lavignen@amazon.com>]

Currently when a malloc_elem is split after resizing, any padding
present in the elem is ignored.  This causes the resized elem to be too
small when padding is present, and user data can overwrite the beginning
of the following malloc_elem.

Solve this by including the size of the padding when computing where to
split the malloc_elem.

Fixes: af75078fece3 ("first public release")

Signed-off-by: Jamie Lavigne <lavignen@amazon.com>
---
 lib/librte_eal/common/malloc_elem.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/lib/librte_eal/common/malloc_elem.c b/lib/librte_eal/common/malloc_elem.c
index 42568e1..08516af 100644
--- a/lib/librte_eal/common/malloc_elem.c
+++ b/lib/librte_eal/common/malloc_elem.c
@@ -314,17 +314,16 @@ malloc_elem_free(struct malloc_elem *elem)
 int
 malloc_elem_resize(struct malloc_elem *elem, size_t size)
 {
-	const size_t new_size = size + MALLOC_ELEM_OVERHEAD;
+	const size_t new_size = size + elem->pad + MALLOC_ELEM_OVERHEAD;
 	/* if we request a smaller size, then always return ok */
-	const size_t current_size = elem->size - elem->pad;
-	if (current_size >= new_size)
+	if (elem->size >= new_size)
 		return 0;
 
 	struct malloc_elem *next = RTE_PTR_ADD(elem, elem->size);
 	rte_spinlock_lock(&elem->heap->lock);
 	if (next ->state != ELEM_FREE)
 		goto err_return;
-	if (current_size + next->size < new_size)
+	if (elem->size + next->size < new_size)
 		goto err_return;
 
 	/* we now know the element fits, so remove from free list,
@@ -333,7 +332,7 @@ malloc_elem_resize(struct malloc_elem *elem, size_t size)
 	elem_free_list_remove(next);
 	join_elem(elem, next);
 
-	if (elem->size - new_size >= MIN_DATA_SIZE + MALLOC_ELEM_OVERHEAD){
+	if (elem->size - new_size >= MIN_DATA_SIZE + MALLOC_ELEM_OVERHEAD) {
 		/* now we have a big block together. Lets cut it down a bit, by splitting */
 		struct malloc_elem *split_pt = RTE_PTR_ADD(elem, new_size);
 		split_pt = RTE_PTR_ALIGN_CEIL(split_pt, RTE_CACHE_LINE_SIZE);
-- 
2.7.3.AMZN