Re: [PATCH v3] dmaengine: nbpfaxi: Fix setting channel irqs in probe()

[Taedcke, Christian]

On 7/9/2026 12:38 PM, Dan Carpenter wrote:
> On Fri, Jul 03, 2026 at 09:56:12AM +0200, Christian Taedcke via B4 Relay wrote:
>> From: Christian Taedcke <christian.taedcke@xxxxxxxxxxxxxxx>
>>
>> When one irq is used for errors and each channel gets a dedicated irq,
>> the total number of irqs is num_channels + 1. If the error irq is not
>> the last entry in irqbuf[] but an earlier one, the loop assigning
>> per-channel irqs terminates one iteration too early and the last
>> channel is left without an irq.
>>
>> Iterate over all collected irqs instead of num_channels so the
>> error-irq skip does not shorten the effective channel count.
>>
>> Fixes: 188c6ba1dd92 ("dmaengine: nbpfaxi: Fix memory corruption in probe()")
>> Cc: stable@xxxxxxxxxxxxxxx
>> Signed-off-by: Christian Taedcke <christian.taedcke@xxxxxxxxxxxxxxx>
>> ---
>> Changes in v3:
>> - Guard against out-of-bound writes to chan in case of an invalid eirq.
>> - Link to v2: https://patch.msgid.link/20260702-upstreaming-nbpfaxi-v1-v2-1-e6d6b178a278@xxxxxxxxxxxxxxx
>>
>> Changes in v2:
>> - Advance chan only when assigning a real irq to fix out-of-bounds
>>   memory access.
>> - Remove now redundant ARRAY_SIZE(irqbuf) check.
>> - Link to v1: https://patch.msgid.link/20260702-upstreaming-nbpfaxi-v1-v1-1-fd8ea8830cea@xxxxxxxxxxxxxxx
>>
>> To: christian.taedcke-oss@xxxxxxxxxxxxxxx
>> To: Vinod Koul <vkoul@xxxxxxxxxx>
>> To: Frank Li <Frank.Li@xxxxxxxxxx>
>> To: Dan Carpenter <error27@xxxxxxxxx>
>> Cc: dmaengine@xxxxxxxxxxxxxxx
>> Cc: linux-kernel@xxxxxxxxxxxxxxx
>> ---
>>  drivers/dma/nbpfaxi.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/dma/nbpfaxi.c b/drivers/dma/nbpfaxi.c
>> index 05d7321629cc..b1f06f0bd0d5 100644
>> --- a/drivers/dma/nbpfaxi.c
>> +++ b/drivers/dma/nbpfaxi.c
>> @@ -1374,14 +1374,14 @@ static int nbpf_probe(struct platform_device *pdev)
>>  		if (irqs == num_channels + 1) {
>>  			struct nbpf_channel *chan;
>>  
>> -			for (i = 0, chan = nbpf->chan; i < num_channels;
>> -			     i++, chan++) {
>> +			for (i = 0, chan = nbpf->chan; i < irqs; i++) {
>>  				/* Skip the error IRQ */
>>  				if (irqbuf[i] == eirq)
>> -					i++;
>> -				if (i >= ARRAY_SIZE(irqbuf))
>> +					continue;
>> +				if (chan >= nbpf->chan + num_channels)
> 
> Prefer my check, but sure...

I tested changing the condition back to check for i. But after a few different approaches, i think the check in v3 (chan >= nbpf->chan + num_channels) is more robust.

It handles the following cases well:
1. eirq is the last entry in irqbuf[]
2. eirq is not in irqbuf[] (which is not expected)

This check also makes it clear that the write destination is verified.

-> i would prefer to keep the v3 patch as is.

> 
> It's pretty annoying that sashiko bot doesn't CC the CC list.
> 
> regards,
> dan carpenter
> 
>>  					return -EINVAL;
>>  				chan->irq = irqbuf[i];
>> +				chan++;
>>  			}
>>  		} else {
>>  			/* 2 IRQs and more than one channel */
> 

Regards,
Christian