[PATCH net] ptr_ring: prevent integer overflow when calculating size

[Jason Wang]

Switch to use dividing to prevent integer overflow when size is too
big to calculate allocation size properly.

Reported-by: Eric Biggers <ebiggers3@xxxxxxxxx>
Fixes: 6e6e41c31122 ("ptr_ring: fail early if queue occupies more than KMALLOC_MAX_SIZE")
Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
---
 include/linux/ptr_ring.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
index b884b77..e633522 100644
--- a/include/linux/ptr_ring.h
+++ b/include/linux/ptr_ring.h
@@ -469,7 +469,7 @@ static inline int ptr_ring_consume_batched_bh(struct ptr_ring *r,
  */
 static inline void **__ptr_ring_init_queue_alloc(unsigned int size, gfp_t gfp)
 {
-	if (size * sizeof(void *) > KMALLOC_MAX_SIZE)
+	if (size > KMALLOC_MAX_SIZE / sizeof(void *))
 		return NULL;
 	return kvmalloc_array(size, sizeof(void *), gfp | __GFP_ZERO);
 }
-- 
2.7.4