Subject: Re: [PATCH] knav_qmss_queue: fix a missing-check bug in knav_pool_create()

From: Gen Zhang <[email-masked]>
Date: Tue, 11 Jun 2019 03:08:19 -0700

On Tue, Jun 11, 2019 at 10:54:15AM +0100, Marc Zyngier wrote:
> Hi Gen,
> 
> No idea why I'm being cc'd on this but hey... ;-)
I copied email address ftom thid commit:-)
https://github.com/torvalds/linux/commit/832ad0e3da4510fd17f98804abe512ea9a747035#diff-f2a24befc247191f4b81af93e9336785
> 
> On 11/06/2019 10:37, Gen Zhang wrote:
> > On Thu, May 30, 2019 at 11:39:49AM +0800, Gen Zhang wrote:
> >> In knav_pool_create(), 'pool->name' is allocated by kstrndup(). It
> >> returns NULL when fails. So 'pool->name' should be checked. And free
> >> 'pool' when error.
> >>
> >> Signed-off-by: Gen Zhang <[email-masked]>
> >> ---
> >> diff --git a/drivers/soc/ti/knav_qmss_queue.c b/drivers/soc/ti/knav_qmss_queue.c
> >> index 8b41837..0f8cb28 100644
> >> --- a/drivers/soc/ti/knav_qmss_queue.c
> >> +++ b/drivers/soc/ti/knav_qmss_queue.c
> >> @@ -814,6 +814,12 @@ void *knav_pool_create(const char *name,
> >>  	}
> >>  
> >>  	pool->name = kstrndup(name, KNAV_NAME_SIZE - 1, GFP_KERNEL);
> >> +	if (!pool->name) {
> >> +		dev_err(kdev->dev, "failed to duplicate for pool(%s)\n",
> >> +			name);
> 
> There is no need to output anything, the kernel will be loud enough if
> you run out of memory.
Thanks for your comments.
> 
> >> +		ret = -ENOMEM;
> >> +		goto err_name;
> >> +	}
> >>  	pool->kdev = kdev;
> >>  	pool->dev = kdev->dev;
> >>  
> >> @@ -864,6 +870,7 @@ void *knav_pool_create(const char *name,
> >>  	mutex_unlock(&knav_dev_lock);
> >>  err:
> >>  	kfree(pool->name);
> >> +err_name:
> 
> kfree(NULL) is perfectly valid, there is no need to create a second
> label. Just branch to the existing error label.
Sure, better not to add redundant codes.
> 
> >>  	devm_kfree(kdev->dev, pool);
> >>  	return ERR_PTR(ret);
> >>  }
> > Can anyone look into this patch?
> > 
> > Thanks
> > Gen
> > 
> 
> The real question is whether this is actually an error at all.
> pool->name doesn't seem to be used for anything but debug information,
> and the printing code can perfectly accommodate a NULL pointer.
That sounds reasonable. This patch just fixes a *theoretical* bug.

Thanks
Gen
> 
> Thanks,
> 
> 	M.
> -- 
> Jazz is not dead. It just smells funny...

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