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atm: idt77252: avoid accessing the data mapped to streaming DMA 

In queue_skb(), skb->data is mapped to streaming DMA on line 850:
  dma_map_single(..., skb->data, ...);

Then skb->data is accessed on lines 862 and 863:
  tbd->word_4 = (skb->data[0] << 24) | (skb->data[1] << 16) |
           (skb->data[2] <<  8) | (skb->data[3] <<  0);
and on lines 893 and 894:
  tbd->word_4 = (skb->data[0] << 24) | (skb->data[1] << 16) |
           (skb->data[2] <<  8) | (skb->data[3] <<  0);

These accesses may cause data inconsistency between CPU cache and
hardware.

To fix this problem, the calculation result of skb->data is stored in a
local variable before DMA mapping, and then the driver accesses this
local variable instead of skb->data.

Signed-off-by: Jia-Ju Bai <baijiaju@tsinghua.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jia-Ju Bai 2020-08-02 17:33:40 +08:00 committed by David S. Miller
parent a45a9e8a76
commit cbbb64f62a
1 changed files with 5 additions and 4 deletions
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9
drivers/atm/idt77252.c
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@ -835,6 +835,7 @@ queue_skb(struct idt77252_dev *card, struct vc_map *vc,
unsigned long flags;
int error;
int aal;
u32 word4;
if (skb->len == 0) {
printk("%s: invalid skb->len (%d)\n", card->name, skb->len);
@ -846,6 +847,8 @@ queue_skb(struct idt77252_dev *card, struct vc_map *vc,
tbd = &IDT77252_PRV_TBD(skb);
vcc = ATM_SKB(skb)->vcc;
word4 = (skb->data[0] << 24) | (skb->data[1] << 16) |
(skb->data[2] << 8) | (skb->data[3] << 0);
IDT77252_PRV_PADDR(skb) = dma_map_single(&card->pcidev->dev, skb->data,
skb->len, DMA_TO_DEVICE);
@ -859,8 +862,7 @@ queue_skb(struct idt77252_dev *card, struct vc_map *vc,
tbd->word_1 = SAR_TBD_OAM | ATM_CELL_PAYLOAD | SAR_TBD_EPDU;
tbd->word_2 = IDT77252_PRV_PADDR(skb) + 4;
tbd->word_3 = 0x00000000;
tbd->word_4 = (skb->data[0] << 24) | (skb->data[1] << 16) |
(skb->data[2] << 8) | (skb->data[3] << 0);
tbd->word_4 = word4;
if (test_bit(VCF_RSV, &vc->flags))
vc = card->vcs[0];
@ -890,8 +892,7 @@ queue_skb(struct idt77252_dev *card, struct vc_map *vc,
tbd->word_2 = IDT77252_PRV_PADDR(skb) + 4;
tbd->word_3 = 0x00000000;
tbd->word_4 = (skb->data[0] << 24) | (skb->data[1] << 16) |
(skb->data[2] << 8) | (skb->data[3] << 0);
tbd->word_4 = word4;
break;
case ATM_AAL5: