lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Mon, 21 Jul 2014 10:44:15 +0200
From:	Javier Martinez Canillas <>
To:	Lars-Peter Clausen <>,
	Dan Williams <>
CC:	Vinod Koul <>,,
Subject: Re: [PATCH 1/1] dmaengine: pl330: Check if the DMA descriptor is

On 07/21/2014 10:22 AM, Lars-Peter Clausen wrote:
> On 07/20/2014 07:58 PM, Javier Martinez Canillas wrote:
>> If this should not really happen and this patch is only a workaround since the
>> bug is elsewhere, please give me some hints and I'll try to fix it properly. I'm
>> not familiar with the PL330 DMA controller but just found what was the NULL
>> pointer being dereferenced and looked at your changes to see what was different now.
> I think the patch is fine as a quick workaround since it is simple and the 
> previous commit broke previously working code.

Agreed, it matches what the old code was doing and other code is relying on this
behavior so works as a quick fix to avoid the current kernel oops.

> The long term fix is to stop calling dma_pl330_rqcb() from 
> pl330_release_channel(). The first thing is you wouldn't expect any transfer 
> to be active when the channel is released. And even if it was by accident we 
> should not call the descriptor callback, but rather but it just back onto 
> the descriptor pool.

Thanks a lot for the clarification. I thought it was something along the lines
of not calling the callback from pl330_release_channel() but preferred to not
change anything that I could not completely understand its side effects.

I'll study the driver more deeply and try to come up with a patch on top of this
one that fixes the actual cause rather than the consequence.

> - Lars

Best regards,
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists