netdev - [PATCH v1] gve: fix the wrong AdminQ buffer overflow check

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Date:   Wed, 14 Jul 2021 15:34:59 +0800
From:   Haiyue Wang <haiyue.wang@...el.com>
To:     netdev@...r.kernel.org
Cc:     Haiyue Wang <haiyue.wang@...el.com>,
        Catherine Sullivan <csully@...gle.com>,
        Sagi Shahar <sagis@...gle.com>,
        Jon Olson <jonolson@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        David Awogbemila <awogbemila@...gle.com>,
        Yangchun Fu <yangchun@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Bailey Forrest <bcf@...gle.com>, Kuo Zhao <kuozhao@...gle.com>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v1] gve: fix the wrong AdminQ buffer overflow check

The 'tail' pointer is also free-running count, so it needs to be masked
as 'adminq_prod_cnt' does, to become an index value of AdminQ buffer.

Fixes: 5cdad90de62c ("gve: Batch AQ commands for creating and destroying queues.")
Signed-off-by: Haiyue Wang <haiyue.wang@...el.com>
---
 drivers/net/ethernet/google/gve/gve_adminq.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/google/gve/gve_adminq.c b/drivers/net/ethernet/google/gve/gve_adminq.c
index 5bb56b454541..f089d33dd48e 100644
--- a/drivers/net/ethernet/google/gve/gve_adminq.c
+++ b/drivers/net/ethernet/google/gve/gve_adminq.c
@@ -322,7 +322,8 @@ static int gve_adminq_issue_cmd(struct gve_priv *priv,
 	tail = ioread32be(&priv->reg_bar0->adminq_event_counter);
 
 	// Check if next command will overflow the buffer.
-	if (((priv->adminq_prod_cnt + 1) & priv->adminq_mask) == tail) {
+	if (((priv->adminq_prod_cnt + 1) & priv->adminq_mask) ==
+	    (tail & priv->adminq_mask)) {
 		int err;
 
 		// Flush existing commands to make room.
@@ -332,7 +333,8 @@ static int gve_adminq_issue_cmd(struct gve_priv *priv,
 
 		// Retry.
 		tail = ioread32be(&priv->reg_bar0->adminq_event_counter);
-		if (((priv->adminq_prod_cnt + 1) & priv->adminq_mask) == tail) {
+		if (((priv->adminq_prod_cnt + 1) & priv->adminq_mask) ==
+		    (tail & priv->adminq_mask)) {
 			// This should never happen. We just flushed the
 			// command queue so there should be enough space.
 			return -ENOMEM;
-- 
2.32.0