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

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Date:   Tue, 5 May 2020 19:02:33 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     davem@...emloft.net, kuba@...nel.org,
        christophe.jaillet@...adoo.fr, leon@...nel.org, tglx@...utronix.de,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [BUG] net: chelsio: Possible buffer overflow caused by DMA
 failures/attacks

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