linux-kernel - Re: [PATCH 14/19] gpu: drm: selftests: test-drm_dp_mst_helper: Place 'struct drm_dp_sideband_msg_req

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Message-ID: <bf216efdf7eea393d6ce5244f7b7a8970c23c235.camel@redhat.com>
Date:   Fri, 06 Nov 2020 14:17:25 -0500
From:   Lyude Paul <lyude@...hat.com>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     linux-kernel@...r.kernel.org, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        David Francis <David.Francis@....com>,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 14/19] gpu: drm: selftests: test-drm_dp_mst_helper:
 Place 'struct drm_dp_sideband_msg_req_body' onto the heap

On Thu, 2020-11-05 at 14:45 +0000, Lee Jones wrote:
> The stack is too full.
> 
> Fixes the following W=1 kernel build warning(s):
> 
>  drivers/gpu/drm/selftests/test-drm_dp_mst_helper.c: In function
> ‘sideband_msg_req_encode_decode’:
>  drivers/gpu/drm/selftests/test-drm_dp_mst_helper.c:161:1: warning: the frame
> size of 1176 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> 
> Cc: David Airlie <airlied@...ux.ie>
> Cc: Daniel Vetter <daniel@...ll.ch>
> Cc: Lyude Paul <lyude@...hat.com>
> Cc: David Francis <David.Francis@....com>
> Cc: dri-devel@...ts.freedesktop.org
> Signed-off-by: Lee Jones <lee.jones@...aro.org>
> ---
>  .../drm/selftests/test-drm_dp_mst_helper.c    | 29 ++++++++++++-------
>  1 file changed, 18 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/selftests/test-drm_dp_mst_helper.c
> b/drivers/gpu/drm/selftests/test-drm_dp_mst_helper.c
> index 1d696ec001cff..0a539456f6864 100644
> --- a/drivers/gpu/drm/selftests/test-drm_dp_mst_helper.c
> +++ b/drivers/gpu/drm/selftests/test-drm_dp_mst_helper.c
> @@ -120,44 +120,51 @@ sideband_msg_req_equal(const struct
> drm_dp_sideband_msg_req_body *in,
>  static bool
>  sideband_msg_req_encode_decode(struct drm_dp_sideband_msg_req_body *in)
>  {
> -       struct drm_dp_sideband_msg_req_body out = {0};
> +       struct drm_dp_sideband_msg_req_body *out;
>         struct drm_printer p = drm_err_printer(PREFIX_STR);
>         struct drm_dp_sideband_msg_tx txmsg;
>         int i, ret;
> +       bool result = true;
> +
> +       out = kzalloc(sizeof(*out), GFP_KERNEL);
> 

You're missing a NULL check here

>  
>         drm_dp_encode_sideband_req(in, &txmsg);
> -       ret = drm_dp_decode_sideband_req(&txmsg, &out);
> +       ret = drm_dp_decode_sideband_req(&txmsg, out);
>         if (ret < 0) {
>                 drm_printf(&p, "Failed to decode sideband request: %d\n",
>                            ret);
> -               return false;
> +               result = false;
> +               goto out;
>         }
>  
> -       if (!sideband_msg_req_equal(in, &out)) {
> +       if (!sideband_msg_req_equal(in, out)) {
>                 drm_printf(&p, "Encode/decode failed, expected:\n");
>                 drm_dp_dump_sideband_msg_req_body(in, 1, &p);
>                 drm_printf(&p, "Got:\n");
> -               drm_dp_dump_sideband_msg_req_body(&out, 1, &p);
> -               return false;
> +               drm_dp_dump_sideband_msg_req_body(out, 1, &p);
> +               result = false;
> +               goto out;
>         }
>  
>         switch (in->req_type) {
>         case DP_REMOTE_DPCD_WRITE:
> -               kfree(out.u.dpcd_write.bytes);
> +               kfree(out->u.dpcd_write.bytes);
>                 break;
>         case DP_REMOTE_I2C_READ:
> -               for (i = 0; i < out.u.i2c_read.num_transactions; i++)
> -                       kfree(out.u.i2c_read.transactions[i].bytes);
> +               for (i = 0; i < out->u.i2c_read.num_transactions; i++)
> +                       kfree(out->u.i2c_read.transactions[i].bytes);
>                 break;
>         case DP_REMOTE_I2C_WRITE:
> -               kfree(out.u.i2c_write.bytes);
> +               kfree(out->u.i2c_write.bytes);
>                 break;
>         }
>  
>         /* Clear everything but the req_type for the input */
>         memset(&in->u, 0, sizeof(in->u));
>  
> -       return true;
> +out:
> +       kfree(out);
> +       return result;
>  }
>  
>  int igt_dp_mst_sideband_msg_req_decode(void *unused)

-- 
Sincerely,
   Lyude Paul (she/her)
   Software Engineer at Red Hat
   
Note: I deal with a lot of emails and have a lot of bugs on my plate. If you've
asked me a question, are waiting for a review/merge on a patch, etc. and I
haven't responded in a while, please feel free to send me another email to check
on my status. I don't bite!