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ALSA: core: Add snd_card_free_on_error() helper
This is a small helper function to handle the error path more easily
when an error happens during the probe for the device with the
device-managed card. Since devres releases in the reverser order of
the creations, usually snd_card_free() gets called at the last in the
probe error path unless it already reached snd_card_register() calls.
Due to this nature, when a driver expects the resource releases in
card->private_free, this might be called too lately.
As a workaround, one should call the probe like:
static int __some_probe(...) { // do real probe.... }
static int some_probe(...)
{
return snd_card_free_on_error(dev, __some_probe(dev, ...));
}
so that the snd_card_free() is called explicitly at the beginning of
the error path from the probe.
This function will be used in the upcoming fixes to address the
regressions by devres usages.
Fixes: e8ad415b7a
("ALSA: core: Add managed card creation")
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20220412093141.8008-2-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
parent
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@ -284,6 +284,7 @@ int snd_card_disconnect(struct snd_card *card);
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void snd_card_disconnect_sync(struct snd_card *card);
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int snd_card_free(struct snd_card *card);
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int snd_card_free_when_closed(struct snd_card *card);
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int snd_card_free_on_error(struct device *dev, int ret);
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void snd_card_set_id(struct snd_card *card, const char *id);
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int snd_card_register(struct snd_card *card);
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int snd_card_info_init(void);
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@ -209,6 +209,12 @@ static void __snd_card_release(struct device *dev, void *data)
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* snd_card_register(), the very first devres action to call snd_card_free()
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* is added automatically. In that way, the resource disconnection is assured
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* at first, then released in the expected order.
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*
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* If an error happens at the probe before snd_card_register() is called and
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* there have been other devres resources, you'd need to free the card manually
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* via snd_card_free() call in the error; otherwise it may lead to UAF due to
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* devres call orders. You can use snd_card_free_on_error() helper for
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* handling it more easily.
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*/
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int snd_devm_card_new(struct device *parent, int idx, const char *xid,
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struct module *module, size_t extra_size,
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@ -235,6 +241,28 @@ int snd_devm_card_new(struct device *parent, int idx, const char *xid,
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}
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EXPORT_SYMBOL_GPL(snd_devm_card_new);
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/**
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* snd_card_free_on_error - a small helper for handling devm probe errors
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* @dev: the managed device object
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* @ret: the return code from the probe callback
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*
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* This function handles the explicit snd_card_free() call at the error from
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* the probe callback. It's just a small helper for simplifying the error
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* handling with the managed devices.
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*/
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int snd_card_free_on_error(struct device *dev, int ret)
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{
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struct snd_card *card;
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if (!ret)
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return 0;
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card = devres_find(dev, __snd_card_release, NULL, NULL);
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if (card)
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snd_card_free(card);
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return ret;
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}
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EXPORT_SYMBOL_GPL(snd_card_free_on_error);
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static int snd_card_init(struct snd_card *card, struct device *parent,
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int idx, const char *xid, struct module *module,
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size_t extra_size)
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