linux-kernel - Re: [PATCH] vDPA/ifcvf: match pointer check to use

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Date:   Tue, 15 Mar 2022 08:03:26 -0700
From:   Tom Rix <trix@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     jasowang@...hat.com, nathan@...nel.org, ndesaulniers@...gle.com,
        lingshan.zhu@...el.com, sgarzare@...hat.com,
        xieyongji@...edance.com, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] vDPA/ifcvf: match pointer check to use


On 3/15/22 6:28 AM, Michael S. Tsirkin wrote:
> On Tue, Mar 15, 2022 at 05:41:30AM -0700, trix@...hat.com wrote:
>> From: Tom Rix <trix@...hat.com>
>>
>> Clang static analysis reports this issue
>> ifcvf_main.c:49:4: warning: Called function
>>    pointer is null (null dereference)
>>    vf->vring->cb.callback(vring->cb.private);
>>    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> The check
>>    vring = &vf->vring[i];
>>    if (vring->cb.callback)
>>
>> Does not match the use.  Change dereference so they match.
>>
>> Fixes: 79333575b8bd ("vDPA/ifcvf: implement shared IRQ feature")
> Thanks a lot! I squashed this into the offending patch - no point in
> breaking bisect. Pushed to linux. However I'm now
> having second thoughts about applying that patchset - I'd like
> soma analysis explaining how this got through testing.

static analysis is something i do treewide.

There are currently ~2500 issues in linux-next, do not panic! many are 
false positives.

It is pretty easy to setup and once you have a baseline you can filter 
only your files.

Tom

>> Signed-off-by: Tom Rix <trix@...hat.com>
>> ---
>>   drivers/vdpa/ifcvf/ifcvf_main.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c b/drivers/vdpa/ifcvf/ifcvf_main.c
>> index 3b48e717e89f7..4366320fb68d3 100644
>> --- a/drivers/vdpa/ifcvf/ifcvf_main.c
>> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
>> @@ -46,7 +46,7 @@ static irqreturn_t ifcvf_vqs_reused_intr_handler(int irq, void *arg)
>>   	for (i = 0; i < vf->nr_vring; i++) {
>>   		vring = &vf->vring[i];
>>   		if (vring->cb.callback)
>> -			vf->vring->cb.callback(vring->cb.private);
>> +			vring->cb.callback(vring->cb.private);
>>   	}
>>   
>>   	return IRQ_HANDLED;
>> -- 
>> 2.26.3