From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: [PATCH net-next V3 1/6] ptr_ring: support zero length ring Date: Thu, 30 Jun 2016 11:52:54 +0800 Message-ID: <1467258779-3539-2-git-send-email-jasowang@redhat.com> References: <1467258779-3539-1-git-send-email-jasowang@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: brouer@redhat.com, eric.dumazet@gmail.com, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org To: mst@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, davem@davemloft.net Return-path: In-Reply-To: <1467258779-3539-1-git-send-email-jasowang@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Id: netdev.vger.kernel.org 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 --- 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