Re: [PATCH v2 2/2] topology: Fix the missing referenced elem ptr when merging private data

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On Jul 22 2016 11:39, Lin, Mengdong wrote:
-----Original Message-----
From: Takashi Sakamoto [mailto:o-takashi@xxxxxxxxxxxxx]
Sent: Friday, July 22, 2016 10:16 AM
To: mengdong.lin@xxxxxxxxxxxxxxx; alsa-devel@xxxxxxxxxxxxxxxx;
broonie@xxxxxxxxxx
Cc: tiwai@xxxxxxx; Lin, Mengdong; Girdwood, Liam R; Nc, Shreyas
Subject: Re: [PATCH v2 2/2] topology: Fix the missing referenced elem ptr
when merging private data

On Jul 22 2016 10:47, mengdong.lin@xxxxxxxxxxxxxxx wrote:
From: Mengdong Lin <mengdong.lin@xxxxxxxxxxxxxxx>

tplg_copy_data() should set the valid referenced data element pointer
on success. The caller will double check this pointer for all kinds of
references, including controls and data.

Signed-off-by: Mengdong Lin <mengdong.lin@xxxxxxxxxxxxxxx>

diff --git a/src/topology/data.c b/src/topology/data.c index
768fc27..e7793b2 100644
--- a/src/topology/data.c
+++ b/src/topology/data.c
@@ -1078,6 +1078,8 @@ int tplg_copy_data(snd_tplg_t *tplg, struct
tplg_elem *elem,
   	ref_elem->compound_elem = 1;
   	memcpy(priv->data + old_priv_data_size,
   	       ref_elem->data->data, priv_data_size);
+
+	ref->elem = ref_elem;
   	return 0;
   }

Is this really OK when the found topology element has no private data?
In this case, ref->elem has no assignment at return.

No. This is my mistake. Thanks for finding this bug.

ref->elem should still be assigned for this case. I will make it like this:

/* overlook empty private data */
if (!ref_elem->data || !ref_elem->data->size) {
		ref->elem = ref_elem;
          return 0;
}

Let us split data merging code to an explicit function? Then:

if (ref_elem->data != NULL && ref_elem->data->size > 0) {
    err = merge_private_data(elem, ref_elem);
    if (err < 0)
        return err;
}
ref->elem = ref_elem;
return 0;

(Here, I expect compiler optimization to merge the new function to caller implicitly.)


Regards

Takashi Sakamoto
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