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From:   NeilBrown <neilb@suse.de>
To:     "J. Bruce Fields" <bfields@fieldses.org>
Date:   Fri, 17 Jul 2020 11:31:17 +1000
Cc:     Jeff Layton <jlayton@kernel.org>, linux-nfs@vger.kernel.org
Subject: Re: nfs4_show_superblock considered harmful :-)
In-Reply-To: <20200717010301.GC18568@fieldses.org>
References: <871rn38suc.fsf@notabene.neil.brown.name> <20200529220608.GA22758@fieldses.org> <87a71n7dek.fsf@notabene.neil.brown.name> <20200715185456.GE15543@fieldses.org> <20200716171958.GB18568@fieldses.org> <87tuy7vxeb.fsf@notabene.neil.brown.name> <20200717010301.GC18568@fieldses.org>
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On Thu, Jul 16 2020, J. Bruce Fields wrote:

> On Fri, Jul 17, 2020 at 09:43:40AM +1000, NeilBrown wrote:
>> On Thu, Jul 16 2020, J. Bruce Fields wrote:
>> > --- a/fs/nfsd/nfs4state.c
>> > +++ b/fs/nfsd/nfs4state.c
>> > @@ -507,6 +507,16 @@ find_any_file(struct nfs4_file *f)
>> >  	return ret;
>> >  }
>> >=20=20
>> > +static struct nfsd_file *find_deleg_file(struct nfs4_file *f)
>> > +{
>> > +	struct nfsd_file *ret;
>> > +
>> > +	spin_lock(&f->fi_lock);
>> > +	ret =3D nfsd_file_get(f->fi_deleg_file);
>>=20
>> A test on f->fi_deleg_file being non-NULL would make this look safer.
>> It would  also make the subsequent test on the return value appear sane.
>
> Yes, thanks!-b.
>
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index c2a2e56c896d..6e8811e7c134 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -509,10 +509,11 @@ find_any_file(struct nfs4_file *f)
>=20=20
>  static struct nfsd_file *find_deleg_file(struct nfs4_file *f)
>  {
> -	struct nfsd_file *ret;
> +	struct nfsd_file *ret =3D NULL;
>=20=20
>  	spin_lock(&f->fi_lock);
> -	ret =3D nfsd_file_get(f->fi_deleg_file);
> +	if (f->fi_deleg_file)
> +		ret =3D nfsd_file_get(f->fi_deleg_file);
>  	spin_unlock(&f->fi_lock);
>  	return ret;
>  }

Reviewed-by: NeilBrown <neilb@suse.de>

for the whole patch.
Thanks,
NeilBrown

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