atm: idt77252: avoid accessing the data mapped to streaming DMA (cbbb64f6) · Commits · 戴 / test

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>

drivers/atm/idt77252.c

+5 −4

Original line number	Diff line number	Diff line
		@@ -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:

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