* [PATCH] rtl8180: avoid accessing the data mapped to streaming DMA
@ 2020-10-19 2:54 Jia-Ju Bai
2020-10-19 18:43 ` Jakub Kicinski
2020-10-19 22:47 ` Maciej S. Szmigiero
0 siblings, 2 replies; 3+ messages in thread
From: Jia-Ju Bai @ 2020-10-19 2:54 UTC (permalink / raw)
To: kvalo, davem, kuba, vaibhavgupta40, christophe.jaillet
Cc: linux-wireless, netdev, linux-kernel, Jia-Ju Bai
In rtl8180_tx(), skb->data is mapped to streaming DMA on line 476:
mapping = dma_map_single(..., skb->data, ...);
On line 459, skb->data is assigned to hdr after cast:
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
Then hdr->seq_ctrl is accessed on lines 540 and 541:
hdr->seq_ctrl &= cpu_to_le16(IEEE80211_SCTL_FRAG);
hdr->seq_ctrl |= cpu_to_le16(priv->seqno);
These DMA accesses may cause data inconsistency between CPU and hardwre.
To fix this problem, hdr->seq_ctrl is accessed before the DMA mapping.
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
drivers/net/wireless/realtek/rtl818x/rtl8180/dev.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/net/wireless/realtek/rtl818x/rtl8180/dev.c b/drivers/net/wireless/realtek/rtl818x/rtl8180/dev.c
index 2477e18c7cae..cc73014aa5f3 100644
--- a/drivers/net/wireless/realtek/rtl818x/rtl8180/dev.c
+++ b/drivers/net/wireless/realtek/rtl818x/rtl8180/dev.c
@@ -473,6 +473,13 @@ static void rtl8180_tx(struct ieee80211_hw *dev,
prio = skb_get_queue_mapping(skb);
ring = &priv->tx_ring[prio];
+ if (info->flags & IEEE80211_TX_CTL_ASSIGN_SEQ) {
+ if (info->flags & IEEE80211_TX_CTL_FIRST_FRAGMENT)
+ priv->seqno += 0x10;
+ hdr->seq_ctrl &= cpu_to_le16(IEEE80211_SCTL_FRAG);
+ hdr->seq_ctrl |= cpu_to_le16(priv->seqno);
+ }
+
mapping = dma_map_single(&priv->pdev->dev, skb->data, skb->len,
DMA_TO_DEVICE);
@@ -534,13 +541,6 @@ static void rtl8180_tx(struct ieee80211_hw *dev,
spin_lock_irqsave(&priv->lock, flags);
- if (info->flags & IEEE80211_TX_CTL_ASSIGN_SEQ) {
- if (info->flags & IEEE80211_TX_CTL_FIRST_FRAGMENT)
- priv->seqno += 0x10;
- hdr->seq_ctrl &= cpu_to_le16(IEEE80211_SCTL_FRAG);
- hdr->seq_ctrl |= cpu_to_le16(priv->seqno);
- }
-
idx = (ring->idx + skb_queue_len(&ring->queue)) % ring->entries;
entry = &ring->desc[idx];
--
2.17.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] rtl8180: avoid accessing the data mapped to streaming DMA
2020-10-19 2:54 [PATCH] rtl8180: avoid accessing the data mapped to streaming DMA Jia-Ju Bai
@ 2020-10-19 18:43 ` Jakub Kicinski
2020-10-19 22:47 ` Maciej S. Szmigiero
1 sibling, 0 replies; 3+ messages in thread
From: Jakub Kicinski @ 2020-10-19 18:43 UTC (permalink / raw)
To: Jia-Ju Bai
Cc: kvalo, davem, vaibhavgupta40, christophe.jaillet, linux-wireless,
netdev, linux-kernel
On Mon, 19 Oct 2020 10:54:20 +0800 Jia-Ju Bai wrote:
> + if (info->flags & IEEE80211_TX_CTL_ASSIGN_SEQ) {
> + if (info->flags & IEEE80211_TX_CTL_FIRST_FRAGMENT)
> + priv->seqno += 0x10;
> + hdr->seq_ctrl &= cpu_to_le16(IEEE80211_SCTL_FRAG);
> + hdr->seq_ctrl |= cpu_to_le16(priv->seqno);
> + }
> +
> mapping = dma_map_single(&priv->pdev->dev, skb->data, skb->len,
> DMA_TO_DEVICE);
>
> @@ -534,13 +541,6 @@ static void rtl8180_tx(struct ieee80211_hw *dev,
>
> spin_lock_irqsave(&priv->lock, flags);
>
> - if (info->flags & IEEE80211_TX_CTL_ASSIGN_SEQ) {
> - if (info->flags & IEEE80211_TX_CTL_FIRST_FRAGMENT)
> - priv->seqno += 0x10;
You're taking the priv->seqno access and modification from under
priv->lock. Is that okay?
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] rtl8180: avoid accessing the data mapped to streaming DMA
2020-10-19 2:54 [PATCH] rtl8180: avoid accessing the data mapped to streaming DMA Jia-Ju Bai
2020-10-19 18:43 ` Jakub Kicinski
@ 2020-10-19 22:47 ` Maciej S. Szmigiero
1 sibling, 0 replies; 3+ messages in thread
From: Maciej S. Szmigiero @ 2020-10-19 22:47 UTC (permalink / raw)
To: Jia-Ju Bai
Cc: kvalo, davem, kuba, vaibhavgupta40, christophe.jaillet,
linux-wireless, netdev, linux-kernel
On 19.10.2020 04:54, Jia-Ju Bai wrote:
> In rtl8180_tx(), skb->data is mapped to streaming DMA on line 476:
> mapping = dma_map_single(..., skb->data, ...);
>
> On line 459, skb->data is assigned to hdr after cast:
> struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
>
> Then hdr->seq_ctrl is accessed on lines 540 and 541:
> hdr->seq_ctrl &= cpu_to_le16(IEEE80211_SCTL_FRAG);
> hdr->seq_ctrl |= cpu_to_le16(priv->seqno);
>
> These DMA accesses may cause data inconsistency between CPU and hardwre.
>
> To fix this problem, hdr->seq_ctrl is accessed before the DMA mapping.
>
This looks like a bug fix to me, shouldn't this have a Fixes: tag and
be CC'ed to stable@?
Maciej
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-10-19 23:03 UTC | newest]
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2020-10-19 18:43 ` Jakub Kicinski
2020-10-19 22:47 ` Maciej S. Szmigiero
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