[PATCH net-next V3 1/6] ptr_ring: support zero length ring

Jason Wang
2016-06-30T04:01:45Z

Sometimes, we need zero length ring. But current code will crash since
we don't do any check before accessing the ring. This patch fixes this.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
include/linux/ptr_ring.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
index 562a65e..d78b8b8 100644
--- a/include/linux/ptr_ring.h
+++ b/include/linux/ptr_ring.h
@@ -102,7 +102,7 @@ static inline bool ptr_ring_full_bh(struct ptr_ring *r)
*/
static inline int __ptr_ring_produce(struct ptr_ring *r, void *ptr)
{
- if (r->queue[r->producer])
+ if (unlikely(!r->size) || r->queue[r->producer])
return -ENOSPC;

r->queue[r->producer++] = ptr;
@@ -164,7 +164,9 @@ static inline int ptr_ring_produce_bh(struct ptr_ring *r, void *ptr)
*/
static inline void *__ptr_ring_peek(struct ptr_ring *r)
{
- return r->queue[r->consumer];
+ if (likely(r->size))
+ return r->queue[r->consumer];
+ return NULL;
}

/* Note: callers invoking this in a loop must use a compiler barrier,
--
2.7.4