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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Message-ID: <6a79eef26121afa9190de5a021f4edef53fc9651.camel@redhat.com>
Date:   Tue, 16 Nov 2021 16:17:56 -0500
From:   Lyude Paul <lyude@...hat.com>
To:     Yizhuo Zhai <yzhai003@....edu>
Cc:     Ben Skeggs <bskeggs@...hat.com>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
        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.

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