p54: avoid accessing the data mapped to streaming DMA

In p54p_tx(), skb->data is mapped to streaming DMA on line 337:
  mapping = pci_map_single(..., skb->data, ...);

Then skb->data is accessed on line 349:
  desc->device_addr = ((struct p54_hdr *)skb->data)->req_id;

This access may cause data inconsistency between CPU cache and hardware.

To fix this problem, ((struct p54_hdr *)skb->data)->req_id is stored in
a local variable before DMA mapping, and then the driver accesses this
local variable instead of skb->data.

Cc: <stable@vger.kernel.org>
Signed-off-by: Jia-Ju Bai <baijiaju@tsinghua.edu.cn>
Acked-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200802132949.26788-1-baijiaju@tsinghua.edu.cn

diff --git a/drivers/net/wireless/intersil/p54/p54pci.c b/drivers/net/wireless/intersil/p54/p54pci.c
index 94064d7cff52658daed1057ba6752a026c79d2a4..e97ee547b9f39b0d1c6ab02bb5063f45523853fd 100644 (file)
--- a/drivers/net/wireless/intersil/p54/p54pci.c
+++ b/drivers/net/wireless/intersil/p54/p54pci.c
@@ -333,10 +333,12 @@ static void p54p_tx(struct ieee80211_hw *dev, struct sk_buff *skb)
        struct p54p_desc *desc;
        dma_addr_t mapping;
        u32 idx, i;
+       __le32 device_addr;
 
        spin_lock_irqsave(&priv->lock, flags);
        idx = le32_to_cpu(ring_control->host_idx[1]);
        i = idx % ARRAY_SIZE(ring_control->tx_data);
+       device_addr = ((struct p54_hdr *)skb->data)->req_id;
 
        mapping = dma_map_single(&priv->pdev->dev, skb->data, skb->len,
                                 DMA_TO_DEVICE);
@@ -350,7 +352,7 @@ static void p54p_tx(struct ieee80211_hw *dev, struct sk_buff *skb)
 
        desc = &ring_control->tx_data[i];
        desc->host_addr = cpu_to_le32(mapping);
-       desc->device_addr = ((struct p54_hdr *)skb->data)->req_id;
+       desc->device_addr = device_addr;
        desc->len = cpu_to_le16(skb->len);
        desc->flags = 0;