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@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 2 deletions

diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
index 562a65e8bcc0..d78b8b89c707 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,