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author | Takashi Iwai <tiwai@suse.de> | 2022-04-12 12:31:40 +0300 |
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committer | Takashi Iwai <tiwai@suse.de> | 2022-04-12 12:47:57 +0300 |
commit | fee2b871d8d6389c9b4bdf9346a99ccc1c98c9b8 (patch) | |
tree | d2af935d5051059606ef2caf577b899b628c31d3 /sound/core/init.c | |
parent | 264fb03497ec1c7841bba872571bcd11beed57a7 (diff) | |
download | linux-fee2b871d8d6389c9b4bdf9346a99ccc1c98c9b8.tar.xz |
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: e8ad415b7a55 ("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>
Diffstat (limited to 'sound/core/init.c')
-rw-r--r-- | sound/core/init.c | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/sound/core/init.c b/sound/core/init.c index 31ba7024e3ad..726a8353201f 100644 --- a/sound/core/init.c +++ b/sound/core/init.c @@ -209,6 +209,12 @@ static void __snd_card_release(struct device *dev, void *data) * snd_card_register(), the very first devres action to call snd_card_free() * is added automatically. In that way, the resource disconnection is assured * at first, then released in the expected order. + * + * If an error happens at the probe before snd_card_register() is called and + * there have been other devres resources, you'd need to free the card manually + * via snd_card_free() call in the error; otherwise it may lead to UAF due to + * devres call orders. You can use snd_card_free_on_error() helper for + * handling it more easily. */ int snd_devm_card_new(struct device *parent, int idx, const char *xid, struct module *module, size_t extra_size, @@ -235,6 +241,28 @@ int snd_devm_card_new(struct device *parent, int idx, const char *xid, } EXPORT_SYMBOL_GPL(snd_devm_card_new); +/** + * snd_card_free_on_error - a small helper for handling devm probe errors + * @dev: the managed device object + * @ret: the return code from the probe callback + * + * This function handles the explicit snd_card_free() call at the error from + * the probe callback. It's just a small helper for simplifying the error + * handling with the managed devices. + */ +int snd_card_free_on_error(struct device *dev, int ret) +{ + struct snd_card *card; + + if (!ret) + return 0; + card = devres_find(dev, __snd_card_release, NULL, NULL); + if (card) + snd_card_free(card); + return ret; +} +EXPORT_SYMBOL_GPL(snd_card_free_on_error); + static int snd_card_init(struct snd_card *card, struct device *parent, int idx, const char *xid, struct module *module, size_t extra_size) |