[PATCH net-next 7/9] net: hns3: fix a dead loop in hclge_cmd_csq_clean

[Salil Mehta]

From: Huazhong Tan <tanhuazh...@huawei.com>

If head has invlid value then a dead loop can be triggered in
hclge_cmd_csq_clean. This patch adds sanity check for this case.

Fixes: 68c0a5c70614 ("net: hns3: Add HNS3 IMP(Integrated Mgmt Proc) Cmd
Interface Support")
Signed-off-by: Huazhong Tan <tanhuazh...@huawei.com>
Signed-off-by: Peng Li <lipeng...@huawei.com>
Signed-off-by: Salil Mehta <salil.me...@huawei.com>
---
 .../net/ethernet/hisilicon/hns3/hns3pf/hclge_cmd.c    | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_cmd.c 
b/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_cmd.c
index ff13d18..fab7068 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_cmd.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_cmd.c
@@ -31,6 +31,17 @@ static int hclge_ring_space(struct hclge_cmq_ring *ring)
        return ring->desc_num - used - 1;
 }
 
+static int is_valid_csq_clean_head(struct hclge_cmq_ring *ring, int h)
+{
+       int u = ring->next_to_use;
+       int c = ring->next_to_clean;
+
+       if (unlikely(h >= ring->desc_num))
+               return 0;
+
+       return u > c ? (h > c && h <= u) : (h > c || h <= u);
+}
+
 static int hclge_alloc_cmd_desc(struct hclge_cmq_ring *ring)
 {
        int size  = ring->desc_num * sizeof(struct hclge_desc);
@@ -141,6 +152,7 @@ static void hclge_cmd_init_regs(struct hclge_hw *hw)
 
 static int hclge_cmd_csq_clean(struct hclge_hw *hw)
 {
+       struct hclge_dev *hdev = (struct hclge_dev *)hw->back;
        struct hclge_cmq_ring *csq = &hw->cmq.csq;
        u16 ntc = csq->next_to_clean;
        struct hclge_desc *desc;
@@ -149,6 +161,13 @@ static int hclge_cmd_csq_clean(struct hclge_hw *hw)
 
        desc = &csq->desc[ntc];
        head = hclge_read_dev(hw, HCLGE_NIC_CSQ_HEAD_REG);
+       rmb(); /* Make sure head is ready before touch any data */
+
+       if (!is_valid_csq_clean_head(csq, head)) {
+               dev_warn(&hdev->pdev->dev, "wrong head (%d, %d-%d)\n", head,
+                          csq->next_to_use, csq->next_to_clean);
+               return 0;
+       }
 
        while (head != ntc) {
                memset(desc, 0, sizeof(*desc));
-- 
2.7.4