[PATCH] ASoC: meson: Keep link pointers valid on realloc failure

[Linmao Li]

meson_card_reallocate_links() grows the DAI link and private data
arrays with two consecutive krealloc() calls and updates the owner
pointers only after both calls have succeeded.

A successful krealloc() may move the data: it frees the old block and
returns a new one. When that happens for the link array and the second
krealloc() then fails, card->dai_link still points to the block that
krealloc() already freed, and the error path frees the new block too.
The probe error path then calls meson_card_clean_references(), which
dereferences card->dai_link and kfree()s it again, resulting in a
use-after-free and a double free.

Set card->dai_link right after the first krealloc() succeeds and keep
the resized array when the second call fails, so the pointer always
refers to a valid allocation that the normal cleanup path can free.
card->num_links is still updated only on full success, which keeps the
cleanup limited to initialized links.

Fixes: 7864a79f37b5 ("ASoC: meson: add axg sound card support")
Signed-off-by: Linmao Li <lilinmao@xxxxxxxxxx>
---
 sound/soc/meson/meson-card-utils.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/sound/soc/meson/meson-card-utils.c b/sound/soc/meson/meson-card-utils.c
index cdb759b466ad..38c1b2ae227f 100644
--- a/sound/soc/meson/meson-card-utils.c
+++ b/sound/soc/meson/meson-card-utils.c
@@ -52,19 +52,18 @@ int meson_card_reallocate_links(struct snd_soc_card *card,
 	if (!links)
 		goto err_links;
 
+	priv->card.dai_link = links;
+
 	ldata = krealloc(priv->link_data,
 			 num_links * sizeof(*priv->link_data),
 			 GFP_KERNEL | __GFP_ZERO);
 	if (!ldata)
-		goto err_ldata;
+		goto err_links;
 
-	priv->card.dai_link = links;
 	priv->link_data = ldata;
 	priv->card.num_links = num_links;
 	return 0;
 
-err_ldata:
-	kfree(links);
 err_links:
 	dev_err(priv->card.dev, "failed to allocate links\n");
 	return -ENOMEM;