linux-kernel - Re: [PATCH] Staging: iommu: Replace null pointer check with IS_ERR in arm_smmu_domain_alloc

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Message-ID: <CAEKBCKMqe1_ijAygn4n-oy8=WoaN-CoDBK_wgDJNEMTgJPG7gw@mail.gmail.com>
Date: Mon, 23 Sep 2024 09:52:02 +0545
From: Dipendra Khadka <kdipendra88@...il.com>
To: Pranjal Shrivastava <praan@...gle.com>
Cc: will@...nel.org, robin.murphy@....com, joro@...tes.org, 
	baolu.lu@...ux.intel.com, linux-arm-kernel@...ts.infradead.org, 
	iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Staging: iommu: Replace null pointer check with IS_ERR in arm_smmu_domain_alloc_user()

Hi Pranjal,

On Mon, 23 Sept 2024 at 08:55, Pranjal Shrivastava <praan@...gle.com> wrote:
>
> On Sun, Sep 22, 2024 at 03:56:20PM +0000, Dipendra Khadka wrote:
> > The smatch reported following:
> > '''
> > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c:3065 arm_smmu_domain_alloc_user() warn: 'smmu_domain' is an error pointer or valid
> > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c:3068 arm_smmu_domain_alloc_user() error: 'smmu_domain' dereferencing possible ERR_PTR()
> > '''
> >
> > The function arm_smmu_domain_alloc() handles the null pointer after
> > kzalloc and returns ERR_PTR(-ENOMEM).
> >
> > Replacing condition check !smmu_domain with IS_ERR(smmu_domain) and
> > returning smmu_domain.
>
> Hi Dipendra,
>
> Thanks for looking into the code. However, I think this was fixed last
> month by Dan's patch [1] and has been merged in the master branch.
> Please pull the latest. :)
>
> [1]
>  https://lore.kernel.org/linux-arm-kernel/172381875518.1794999.1134549433569030700.b4-ty@kernel.org/T/
>

I just checked on the staging-next. I will make sure to check on this
tree as well.

> >
> > Signed-off-by: Dipendra Khadka <kdipendra88@...il.com>
> > ---
> >  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > index a31460f9f3d4..19c53c6f7578 100644
> > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > @@ -3062,8 +3062,8 @@ arm_smmu_domain_alloc_user(struct device *dev, u32 flags,
> >               return ERR_PTR(-EOPNOTSUPP);
> >
> >       smmu_domain = arm_smmu_domain_alloc();
> > -     if (!smmu_domain)
> > -             return ERR_PTR(-ENOMEM);
> > +     if (IS_ERR(smmu_domain))
> > +             return smmu_domain;
>
> Quick note, using something like `ERR_CAST` is better in such cases.
>

Thanks a lot for the knowledge.

> >
> >       smmu_domain->domain.type = IOMMU_DOMAIN_UNMANAGED;
> >       smmu_domain->domain.ops = arm_smmu_ops.default_domain_ops;
> > --
> > 2.43.0
> >
> >
>
> Thanks,
> Pranjal

Thanks,
Dipendra Khadka