netdev - [PATCH net-next V4 1/6] ptr_ring: support zero length ring

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Date:	Thu, 30 Jun 2016 14:45:31 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	mst@...hat.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, davem@...emloft.net
Cc:	kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
	eric.dumazet@...il.com, brouer@...hat.com,
	Jason Wang <jasowang@...hat.com>
Subject: [PATCH net-next V4 1/6] ptr_ring: support zero length ring

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@...hat.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