[PATCH 5.9 61/74] p54: avoid accessing the data mapped to streaming DMA

Greg Kroah-Hartman
2020-10-31T11:46:41Z

From: Jia-Ju Bai <baijiaju@tsinghua.edu.cn>

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: <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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/net/wireless/intersil/p54/p54pci.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- 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
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

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;