[PATCH] eal: fix modify data area after memset

[Fengnan Chang]

Let's look at this path:
malloc_elem_free
   ->malloc_elem_join_adjacent_free
      ->join_elem(elem, elem->next)

0. cur elem's pad > 0
1. data area memset in malloc_elem_free first.
2. next elem is free, try to join cur elem and next.
3. in join_elem, try to modify inner->size, this address had
memset in step 1, it casue the content of addrees become non-zero.

If user call rte_zmalloc, and pick this elem, it can't get all
zero'd memory.

Fixes: 2808a12cc053 (malloc: fix memory element size in case of padding)
Signed-off-by: Fengnan Chang <changfengnan at bytedance.com>
---
 lib/eal/common/malloc_elem.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/lib/eal/common/malloc_elem.c b/lib/eal/common/malloc_elem.c
index 619c040aa3..93a23fa8d4 100644
--- a/lib/eal/common/malloc_elem.c
+++ b/lib/eal/common/malloc_elem.c
@@ -492,7 +492,7 @@ malloc_elem_alloc(struct malloc_elem *elem, size_t size, unsigned align,
  * be contiguous in memory.
  */
 static inline void
-join_elem(struct malloc_elem *elem1, struct malloc_elem *elem2)
+join_elem(struct malloc_elem *elem1, struct malloc_elem *elem2, bool update_inner)
 {
 	struct malloc_elem *next = elem2->next;
 	elem1->size += elem2->size;
@@ -502,7 +502,7 @@ join_elem(struct malloc_elem *elem1, struct malloc_elem *elem2)
 		elem1->heap->last = elem1;
 	elem1->next = next;
 	elem1->dirty |= elem2->dirty;
-	if (elem1->pad) {
+	if (elem1->pad && update_inner) {
 		struct malloc_elem *inner = RTE_PTR_ADD(elem1, elem1->pad);
 		inner->size = elem1->size - elem1->pad;
 	}
@@ -526,7 +526,7 @@ malloc_elem_join_adjacent_free(struct malloc_elem *elem)
 
 		/* remove from free list, join to this one */
 		malloc_elem_free_list_remove(elem->next);
-		join_elem(elem, elem->next);
+		join_elem(elem, elem->next, false);
 
 		/* erase header, trailer and pad */
 		memset(erase, MALLOC_POISON, erase_len);
@@ -550,7 +550,7 @@ malloc_elem_join_adjacent_free(struct malloc_elem *elem)
 		malloc_elem_free_list_remove(elem->prev);
 
 		new_elem = elem->prev;
-		join_elem(new_elem, elem);
+		join_elem(new_elem, elem, false);
 
 		/* erase header, trailer and pad */
 		memset(erase, MALLOC_POISON, erase_len);
@@ -683,7 +683,7 @@ malloc_elem_resize(struct malloc_elem *elem, size_t size)
 	 * join the two
 	 */
 	malloc_elem_free_list_remove(elem->next);
-	join_elem(elem, elem->next);
+	join_elem(elem, elem->next, true);
 
 	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 */
-- 
2.20.1