This is a note to let you know that I've just added the patch titled p54: avoid accessing the data mapped to streaming DMA to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: p54-avoid-accessing-the-data-mapped-to-streaming-dma.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 478762855b5ae9f68fa6ead1edf7abada70fcd5f Mon Sep 17 00:00:00 2001 From: Jia-Ju Bai <baijiaju@xxxxxxxxxxxxxxx> Date: Sun, 2 Aug 2020 21:29:49 +0800 Subject: p54: avoid accessing the data mapped to streaming DMA From: Jia-Ju Bai <baijiaju@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx> Signed-off-by: Jia-Ju Bai <baijiaju@xxxxxxxxxxxxxxx> Acked-by: Christian Lamparter <chunkeey@xxxxxxxxx> Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20200802132949.26788-1-baijiaju@xxxxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 @@ -332,10 +332,12 @@ 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 = pci_map_single(priv->pdev, skb->data, skb->len, PCI_DMA_TODEVICE); @@ -349,7 +351,7 @@ 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; Patches currently in stable-queue which might be from baijiaju@xxxxxxxxxxxxxxx are queue-4.19/p54-avoid-accessing-the-data-mapped-to-streaming-dma.patch