linux-kernel - Re: [PATCH] In function nvkm_ioctl_map(), the variable "type" could be uninitialized if "nvkm_object_map()" returns error code, however, it does not check the return value and directly use the "type" in the if statement, which is potentially unsafe.

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Date:   Fri, 17 Dec 2021 18:58:04 -0800
From:   Yizhuo Zhai <yzhai003@....edu>
To:     Lyude Paul <lyude@...hat.com>
Cc:     Ben Skeggs <bskeggs@...hat.com>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        nouveau <nouveau@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] In function nvkm_ioctl_map(), the variable "type" could
 be uninitialized if "nvkm_object_map()" returns error code, however, it does
 not check the return value and directly use the "type" in the if statement,
 which is potentially unsafe.

Hi Lyude:
I appreciate your feedback and I misplaced the commit message to the
title, I have modified it and resend the patch.
I made my linux development tree a mess, so I sent a brandly new one
and cc you. Thanks again for your help: )


On Tue, Nov 16, 2021 at 1:18 PM Lyude Paul <lyude@...hat.com> wrote:
>
> This is a very long patch name, it should probably be shorter and the
> details in the patch title moved into the actual commit description
> instead. Also a couple of things aren't formatted correctly:
>
> * Cc tag for stable is missing, see
>   https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
> * Fixes tag isn't formatted properly
>
> I generally recommend using `dim fixes` from
> https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
> in order to get the correct stable kernel CC tag and Fixes: tag (you can
> drop any of the Ccs it gives you beyond the one to stable at vger dot
> kernel dot org.
>
> Also, if you could try to Cc: me on the next version - will help me
> respond faster :).
>
> On Mon, 2021-11-15 at 23:07 -0800, Yizhuo Zhai wrote:
> > Fixes:01326050391ce("drm/nouveau/core/object: allow arguments to
> > be passed to map function")
> > Signed-off-by: Yizhuo Zhai <yzhai003@....edu>
> > ---
> >  drivers/gpu/drm/nouveau/nvkm/core/ioctl.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/nouveau/nvkm/core/ioctl.c
> > b/drivers/gpu/drm/nouveau/nvkm/core/ioctl.c
> > index 735cb6816f10..4264d9d79783 100644
> > --- a/drivers/gpu/drm/nouveau/nvkm/core/ioctl.c
> > +++ b/drivers/gpu/drm/nouveau/nvkm/core/ioctl.c
> > @@ -266,6 +266,8 @@ nvkm_ioctl_map(struct nvkm_client *client,
> >                 ret = nvkm_object_map(object, data, size, &type,
> >                                       &args->v0.handle,
> >                                       &args->v0.length);
> > +               if (ret)
> > +                       return ret;
> >                 if (type == NVKM_OBJECT_MAP_IO)
> >                         args->v0.type = NVIF_IOCTL_MAP_V0_IO;
> >                 else
>
> --
> Cheers,
>  Lyude Paul (she/her)
>  Software Engineer at Red Hat
>


--
Kind Regards,

Yizhuo Zhai

Computer Science, Graduate Student
University of California, Riverside