[BUG] net: chelsio: Possible buffer overflow caused by DMA failures/attacks

[BUG] net: chelsio: Possible buffer overflow caused by DMA failures/attacks

[Jia-Ju Bai]

In alloc_rx_resources():
     sge->respQ.entries =
         pci_alloc_consistent(pdev, size, &sge->respQ.dma_addr);

Thus, "sge->respQ.entries" is a DMA value, and it is assigned to
"e" in process_pure_responses():
     struct sge *sge = adapter->sge;
     struct respQ *q = &sge->respQ;
     struct respQ_e *e = &q->entries[q->cidx];

When DMA failures or attacks occur, the data stored in "e" can be
changed at any time. In this case, the value of "e->FreelistQid"
can be a large number to cause buffer overflow when the
following code is executed:
     const struct freelQ *fl = &sge->freelQ[e->FreelistQid];

Similarly, "sge->respQ.entries" is also assigned to "e" in
process_responses():
     struct sge *sge = adapter->sge;
     struct respQ *q = &sge->respQ;
     struct respQ_e *e = &q->entries[q->cidx];

When DMA failures or attacks occur, the data stored in "e" can be
changed at any time. In this case, the value of "e->FreelistQid"
can be a large number to cause buffer overflow when the
following code is executed:
     struct freelQ *fl = &sge->freelQ[e->FreelistQid];

Considering that DMA can fail or be attacked, I think that it is 
dangerous to
use a DMA value (or any value tainted by it) as an array index or a 
control-flow
condition. However, I have found many such dangerous cases in Linux 
device drivers
through my static-analysis tool and code review.
I am not sure whether my opinion is correct, so I want to listen to your 
points of view.
Thanks in advance :)


Best wishes,
Jia-Ju Bai

Re: [BUG] net: chelsio: Possible buffer overflow caused by DMA failures/attacks

[Greg KH]

On Tue, May 05, 2020 at 11:50:28PM +0800, Jia-Ju Bai wrote:
> In alloc_rx_resources():
>     sge->respQ.entries =
>         pci_alloc_consistent(pdev, size, &sge->respQ.dma_addr);
> 
> Thus, "sge->respQ.entries" is a DMA value, and it is assigned to
> "e" in process_pure_responses():
>     struct sge *sge = adapter->sge;
>     struct respQ *q = &sge->respQ;
>     struct respQ_e *e = &q->entries[q->cidx];
> 
> When DMA failures or attacks occur, the data stored in "e" can be
> changed at any time. In this case, the value of "e->FreelistQid"
> can be a large number to cause buffer overflow when the
> following code is executed:
>     const struct freelQ *fl = &sge->freelQ[e->FreelistQid];
> 
> Similarly, "sge->respQ.entries" is also assigned to "e" in
> process_responses():
>     struct sge *sge = adapter->sge;
>     struct respQ *q = &sge->respQ;
>     struct respQ_e *e = &q->entries[q->cidx];
> 
> When DMA failures or attacks occur, the data stored in "e" can be
> changed at any time. In this case, the value of "e->FreelistQid"
> can be a large number to cause buffer overflow when the
> following code is executed:
>     struct freelQ *fl = &sge->freelQ[e->FreelistQid];
> 
> Considering that DMA can fail or be attacked, I think that it is dangerous
> to
> use a DMA value (or any value tainted by it) as an array index or a
> control-flow
> condition. However, I have found many such dangerous cases in Linux device
> drivers
> through my static-analysis tool and code review.
> I am not sure whether my opinion is correct, so I want to listen to your
> points of view.

Can you create a patch to show what you think needs to be fixed?  That's
the best way to get feedback, reports like this are usually very
infrequently replied to.

thanks,

greg k-h