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References: <20231122093509.34302-1-yaolu@kylinos.cn> <20231123012234.5783-1-yaolu@kylinos.cn>
 <80ea6067-c531-4765-8576-265e565525fa@amd.com>
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From:   Alex Deucher <alexdeucher@gmail.com>
Date:   Mon, 27 Nov 2023 17:20:38 -0500
Message-ID: <CADnq5_M7TjyM5n7X1mvxRzrckd4meVsvJMrMyt-BpciEPcqC-Q@mail.gmail.com>
Subject: Re: [PATCH v2] drm/amdgpu: Fix cat debugfs amdgpu_regs_didt causes
 kernel null pointer
To:     =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>
Cc:     Lu Yao <yaolu@kylinos.cn>, airlied@gmail.com, daniel@ffwll.ch,
        alexander.deucher@amd.com, dri-devel@lists.freedesktop.org,
        amd-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org
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Applied.  Thanks!

Alex

On Thu, Nov 23, 2023 at 3:22=E2=80=AFAM Christian K=C3=B6nig
<christian.koenig@amd.com> wrote:
>
> Am 23.11.23 um 02:22 schrieb Lu Yao:
> > For 'AMDGPU_FAMILY_SI' family cards, in 'si_common_early_init' func, in=
it
> > 'didt_rreg' and 'didt_wreg' to 'NULL'. But in func
> > 'amdgpu_debugfs_regs_didt_read/write', using 'RREG32_DIDT' 'WREG32_DIDT=
'
> > lacks of relevant judgment. And other 'amdgpu_ip_block_version' that us=
e
> > these two definitions won't be added for 'AMDGPU_FAMILY_SI'.
> >
> > So, add null pointer judgment before calling.
> >
> > Signed-off-by: Lu Yao <yaolu@kylinos.cn>
>
> Reviewed-by: Christian K=C3=B6nig <christian.koenig@amd.com>
>
> > ---
> > Changes in v2:
> >    1. Drop dev_err message.
> >    2. Change error code from 'EPERM' to 'EOPNOTSUPP'
> > Link to v1: https://lore.kernel.org/all/20231122093509.34302-1-yaolu@ky=
linos.cn/
> > Thanks Christian for his comments.
> > ---
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c b/drivers/gpu/=
drm/amd/amdgpu/amdgpu_debugfs.c
> > index a53f436fa9f1..e098cd66fa2a 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> > @@ -638,6 +638,9 @@ static ssize_t amdgpu_debugfs_regs_didt_read(struct=
 file *f, char __user *buf,
> >       if (size & 0x3 || *pos & 0x3)
> >               return -EINVAL;
> >
> > +     if (adev->didt_rreg =3D=3D NULL)
> > +             return -EOPNOTSUPP;
> > +
> >       r =3D pm_runtime_get_sync(adev_to_drm(adev)->dev);
> >       if (r < 0) {
> >               pm_runtime_put_autosuspend(adev_to_drm(adev)->dev);
> > @@ -694,6 +697,9 @@ static ssize_t amdgpu_debugfs_regs_didt_write(struc=
t file *f, const char __user
> >       if (size & 0x3 || *pos & 0x3)
> >               return -EINVAL;
> >
> > +     if (adev->didt_wreg =3D=3D NULL)
> > +             return -EOPNOTSUPP;
> > +
> >       r =3D pm_runtime_get_sync(adev_to_drm(adev)->dev);
> >       if (r < 0) {
> >               pm_runtime_put_autosuspend(adev_to_drm(adev)->dev);
>