[PATCH] drivers: atm: eni: Add pci_dma_mapping_error() call

[PATCH] drivers: atm: eni: Add pci_dma_mapping_error() call

[Tina Johnson]

Added a pci_dma_mapping_error() call to check for mapping errors before
further using the dma handle. Unchecked dma handles were found using
Coccinelle:

@rule1@
expression e1;
identifier x;
@@

*x = pci_map_single(...);
 ... when != pci_dma_mapping_error(e1,x)

Signed-off-by: Tina Johnson <tinajohnson.1234@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
---
 drivers/atm/eni.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/atm/eni.c b/drivers/atm/eni.c
index d65975a..6450a36 100644
--- a/drivers/atm/eni.c
+++ b/drivers/atm/eni.c
@@ -356,6 +356,8 @@ static int do_rx_dma(struct atm_vcc *vcc,struct sk_buff *skb,
 	if (skb) {
 		paddr = pci_map_single(eni_dev->pci_dev,skb->data,skb->len,
 		    PCI_DMA_FROMDEVICE);
+		if (pci_dma_mapping_error(eni_dev->pci_dev, paddr))
+			goto trouble;
 		ENI_PRV_PADDR(skb) = paddr;
 		if (paddr & 3)
 			printk(KERN_CRIT DEV_LABEL "(itf %d): VCI %d has "
-- 
1.7.10.4

Re: [PATCH] drivers: atm: eni: Add pci_dma_mapping_error() call

[David Miller]

From: Tina Johnson <tinajohnson.1234@gmail.com>
Date: Sat,  8 Nov 2014 21:48:02 +0530

> Added a pci_dma_mapping_error() call to check for mapping errors before
> further using the dma handle. Unchecked dma handles were found using
> Coccinelle:
> 
> @rule1@
> expression e1;
> identifier x;
> @@
> 
> *x = pci_map_single(...);
>  ... when != pci_dma_mapping_error(e1,x)
> 
> Signed-off-by: Tina Johnson <tinajohnson.1234@gmail.com>
> Acked-by: Julia Lawall <julia.lawall@lip6.fr>

I really don't like quick fixes like this, exactly because of the
kind of new bug this change is introducing.

The 'trouble' label assumes that it is recovering and unwinding state
when an error occurs after the DMA buffer is successfully mapped.

It unconditionally does pci_unmap_single() if 'paddr' is non-zero
which it might be in the error case depending upon how DMA errors
are represented on a given platform.

Re: [PATCH] drivers: atm: eni: Add pci_dma_mapping_error() call

[Tina Johnson]

On Mon, 10 Nov 2014, David Miller wrote:

> The 'trouble' label assumes that it is recovering and unwinding state
> when an error occurs after the DMA buffer is successfully mapped.
>
> It unconditionally does pci_unmap_single() if 'paddr' is non-zero
> which it might be in the error case depending upon how DMA errors
> are represented on a given platform.

Sorry for the trouble and thankyou for your very helpful comment. I
will send the revised patch.