[dpdk-dev] [PATCH 1/2] mem: zero out memory on free

[Sergio Gonzalez Monroy]

Since [1] memzones are not guaranteed to be zeroed out.
This could potentially cause issues as applications might have been
relying on the allocated memory being zeroed out.

On init all allocated memory is zeroed by the kernel, so by zeroing out
memory on free, all available dpdk memory is always zeroed.

[1] fafcc11985a2 ("mem: rework memzone to be allocated by malloc")

Signed-off-by: Sergio Gonzalez Monroy <sergio.gonzalez.monroy at intel.com>
---
 lib/librte_eal/common/malloc_elem.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/lib/librte_eal/common/malloc_elem.c b/lib/librte_eal/common/malloc_elem.c
index 27e9925..42568e1 100644
--- a/lib/librte_eal/common/malloc_elem.c
+++ b/lib/librte_eal/common/malloc_elem.c
@@ -275,11 +275,14 @@ malloc_elem_free(struct malloc_elem *elem)
 		return -1;
 
 	rte_spinlock_lock(&(elem->heap->lock));
+	size_t sz = elem->size - sizeof(*elem);
+	uint8_t *ptr = (uint8_t *)&elem[1];
 	struct malloc_elem *next = RTE_PTR_ADD(elem, elem->size);
 	if (next->state == ELEM_FREE){
 		/* remove from free list, join to this one */
 		elem_free_list_remove(next);
 		join_elem(elem, next);
+		sz += sizeof(*elem);
 	}
 
 	/* check if previous element is free, if so join with it and return,
@@ -288,15 +291,17 @@ malloc_elem_free(struct malloc_elem *elem)
 	if (elem->prev != NULL && elem->prev->state == ELEM_FREE) {
 		elem_free_list_remove(elem->prev);
 		join_elem(elem->prev, elem);
-		malloc_elem_free_list_insert(elem->prev);
-	}
-	/* otherwise add ourselves to the free list */
-	else {
-		malloc_elem_free_list_insert(elem);
-		elem->pad = 0;
+		sz += sizeof(*elem);
+		ptr -= sizeof(*elem);
+		elem = elem->prev;
 	}
+	malloc_elem_free_list_insert(elem);
+
 	/* decrease heap's count of allocated elements */
 	elem->heap->alloc_count--;
+
+	memset(ptr, 0, sz);
+
 	rte_spinlock_unlock(&(elem->heap->lock));
 
 	return 0;
-- 
2.4.11