Commit 9f9dc704 authored by Jia-Ju Bai's avatar Jia-Ju Bai Committed by Greg Kroah-Hartman
Browse files

p54: avoid accessing the data mapped to streaming DMA

commit 478762855b5ae9f68fa6ead1edf7abada70fcd5f upstream.

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: <>
Signed-off-by: default avatarJia-Ju Bai <>
Acked-by: default avatarChristian Lamparter <>
Signed-off-by: default avatarKalle Valo <>

Signed-off-by: default avatarGreg Kroah-Hartman <>
parent 9f4ef6a9
......@@ -329,10 +329,12 @@ 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 = pci_map_single(priv->pdev, skb->data, skb->len,
......@@ -346,7 +348,7 @@ 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;
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