[PATCH] ASoC: apple: mca: Annotate struct mca_data with __counted_by

[Kees Cook]

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct mca_data.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: "Martin Povišer" <povik+lin@xxxxxxxxxxx>
Cc: Liam Girdwood <lgirdwood@xxxxxxxxx>
Cc: Mark Brown <broonie@xxxxxxxxxx>
Cc: Jaroslav Kysela <perex@xxxxxxxx>
Cc: Takashi Iwai <tiwai@xxxxxxxx>
Cc: asahi@xxxxxxxxxxxxxxx
Cc: alsa-devel@xxxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 sound/soc/apple/mca.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/soc/apple/mca.c b/sound/soc/apple/mca.c
index ce77934f3eef..99e547ef95e6 100644
--- a/sound/soc/apple/mca.c
+++ b/sound/soc/apple/mca.c
@@ -161,7 +161,7 @@ struct mca_data {
 	struct mutex port_mutex;
 
 	int nclusters;
-	struct mca_cluster clusters[];
+	struct mca_cluster clusters[] __counted_by(nclusters);
 };
 
 static void mca_modify(struct mca_cluster *cl, int regoffset, u32 mask, u32 val)
-- 
2.34.1