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

[santosh . shilimkar]

On 6/11/19 3:08 AM, Gen Zhang wrote:
> 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 <blackgod016574@xxxxxxxxx>
> > > > ---
> > > > 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.
Not even theoretical bug.