If asoc_simple_card_probe() fails, asoc_simple_card_unref() may be called before dev_set_drvdata(), causing a NULL pointer dereference in asoc_simple_card_unref():
Unable to handle kernel NULL pointer dereference at virtual address 000000d4 ... PC is at asoc_simple_card_unref+0x14/0x48 LR is at asoc_simple_card_probe+0x3d4/0x40c
This typically happens because asoc_simple_card_parse_of() returns -EPROBE_DEFER, but other failure modes are possible. devm_snd_soc_register_card()/snd_soc_register_card() may fail either before or after dev_set_drvdata().
Pass a snd_soc_card pointer instead of a platform_device pointer to asoc_simple_card_unref() to fix this.
Note that if CONFIG_OF_DYNAMIC=n, of_node_put() is a dummy, and gcc may optimize away the loop over card->dai_link, never actually dereferencing card, and thus avoiding the crash...
Signed-off-by: Geert Uytterhoeven geert+renesas@glider.be Fixes: e512e001dafa54e5 ("ASoC: simple-card: Fix the reference count of device nodes") --- Seen on sh73a0/kzm9g-multiplatform and r8a7740/armadillo-multiplatform, first with CONFIG_OF_DYNAMIC=y, later with extra debug code that caused the loop not to be optimized away. It took me a while to understand what was really happening...
I think this should be applied to -stable.
In v3.15 and v3.16, only 8xx, pseries, and wsp selected OF_DYNAMIC, and I believe they don't use aSoC? In v3.17 and later, OF_DYNAMIC is selected by OF_SELFTEST/OF_UNITTEST. --- sound/soc/generic/simple-card.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/sound/soc/generic/simple-card.c b/sound/soc/generic/simple-card.c index fb9240fdc9b70095..7fe3009b1c43c63c 100644 --- a/sound/soc/generic/simple-card.c +++ b/sound/soc/generic/simple-card.c @@ -452,9 +452,8 @@ static int asoc_simple_card_parse_of(struct device_node *node, }
/* Decrease the reference count of the device nodes */ -static int asoc_simple_card_unref(struct platform_device *pdev) +static int asoc_simple_card_unref(struct snd_soc_card *card) { - struct snd_soc_card *card = platform_get_drvdata(pdev); struct snd_soc_dai_link *dai_link; int num_links;
@@ -556,7 +555,7 @@ static int asoc_simple_card_probe(struct platform_device *pdev) return ret;
err: - asoc_simple_card_unref(pdev); + asoc_simple_card_unref(&priv->snd_card); return ret; }
@@ -572,7 +571,7 @@ static int asoc_simple_card_remove(struct platform_device *pdev) snd_soc_jack_free_gpios(&simple_card_mic_jack, 1, &simple_card_mic_jack_gpio);
- return asoc_simple_card_unref(pdev); + return asoc_simple_card_unref(card); }
static const struct of_device_id asoc_simple_of_match[] = {