mem: fix overflow on allocation

The size checking is done in the caller. The size parameter is an
unsigned (64b wide) right now, so the comparison with zero should be
enough in most cases. But it won't help in the following case.
If the allocating request input a huge number by mistake, e.g., some
overflow after the calculation (especially subtraction), the checking
in the caller will succeed since it is not zero. Indeed, there is not
enough space in the system to support such huge memory allocation.
Usually it will return failure in the following code. But if the
input size is just a little smaller than the UINT64_MAX, like -2 in
signed type.
The roundup will cause an overflow and then "reset" the size to 0,
and then only a header (128B now) with zero length will be returned.
The following will be the previous allocation header.
It should be OK in most cases if the application won't access the
memory body. Or else, some critical issue will be caused and not easy
to debug. So this issue should be prevented at the beginning, like
other big size failure, NULL pointer should be returned also.

Fixes: fdf20fa7be ("add prefix to cache line macros")
Cc: stable@dpdk.org

Signed-off-by: Bing Zhao <bingz@mellanox.com>
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>

app/test/test_malloc.c

@@ -846,6 +846,18 @@ test_malloc_bad_params(void)
 	if (bad_ptr != NULL)
 		goto err_return;
 
+	/* rte_malloc expected to return null with size will cause overflow */
+	align = RTE_CACHE_LINE_SIZE;
+	size = (size_t)-8;
+
+	bad_ptr = rte_malloc(type, size, align);
+	if (bad_ptr != NULL)
+		goto err_return;
+
+	bad_ptr = rte_realloc(NULL, size, align);
+	if (bad_ptr != NULL)
+		goto err_return;
+
 	return 0;
 
 err_return:

lib/librte_eal/common/malloc_heap.c

@@ -241,6 +241,9 @@ heap_alloc(struct malloc_heap *heap, const char *type __rte_unused, size_t size,
 	size = RTE_CACHE_LINE_ROUNDUP(size);
 	align = RTE_CACHE_LINE_ROUNDUP(align);
 
+	/* roundup might cause an overflow */
+	if (size == 0)
+		return NULL;
 	elem = find_suitable_element(heap, size, flags, align, bound, contig);
 	if (elem != NULL) {
 		elem = malloc_elem_alloc(elem, size, align, bound, contig);