linux-kernel - [PATCH v2] gve: fix the wrong AdminQ buffer queue index check

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Message-Id: <20220128104716.9020-1-haiyue.wang@intel.com>
Date:   Fri, 28 Jan 2022 18:47:14 +0800
From:   Haiyue Wang <haiyue.wang@...el.com>
To:     netdev@...r.kernel.org
Cc:     Haiyue Wang <haiyue.wang@...el.com>,
        Jeroen de Borst <jeroendb@...gle.com>,
        Catherine Sullivan <csully@...gle.com>,
        David Awogbemila <awogbemila@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Bailey Forrest <bcf@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Shailend Chand <shailend@...gle.com>,
        Yangchun Fu <yangchun@...gle.com>,
        Sagi Shahar <sagis@...gle.com>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2] gve: fix the wrong AdminQ buffer queue index check

The 'tail' and 'head' are 'unsigned int' type free-running count, when
'head' is overflow, the 'int i (= tail) < u32 head' will be false:

Only '- loop 0: idx = 63' result is shown, so it needs to use 'int' type
to compare, it can handle the overflow correctly.

typedef uint32_t u32;

int main()
{
        u32 tail, head;
        int stail, shead;
        int i, loop;

        tail = 0xffffffff;
        head = 0x00000000;

        for (i = tail, loop = 0; i < head; i++) {
                unsigned int idx = i & 63;

                printf("+ loop %d: idx = %u\n", loop++, idx);
        }

        stail = tail;
        shead = head;
        for (i = stail, loop = 0; i < shead; i++) {
                unsigned int idx = i & 63;

                printf("- loop %d: idx = %u\n", loop++, idx);
        }

        return 0;
}

Fixes: 5cdad90de62c ("gve: Batch AQ commands for creating and destroying queues.")
Signed-off-by: Haiyue Wang <haiyue.wang@...el.com>
---
v2: Fix empty lines surround the Fixes tag
---
 drivers/net/ethernet/google/gve/gve_adminq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/google/gve/gve_adminq.c b/drivers/net/ethernet/google/gve/gve_adminq.c
index 2ad7f57f7e5b..f7621ab672b9 100644
--- a/drivers/net/ethernet/google/gve/gve_adminq.c
+++ b/drivers/net/ethernet/google/gve/gve_adminq.c
@@ -301,7 +301,7 @@ static int gve_adminq_parse_err(struct gve_priv *priv, u32 status)
  */
 static int gve_adminq_kick_and_wait(struct gve_priv *priv)
 {
-	u32 tail, head;
+	int tail, head;
 	int i;
 
 	tail = ioread32be(&priv->reg_bar0->adminq_event_counter);
-- 
2.35.0