[PATCH 5.15 024/148] ALSA: core: Fix double-free at snd_card_new()

Greg Kroah-Hartman
2022-09-26T11:14:34Z

From: Takashi Iwai <tiwai@suse.de>

commit c3afa2a402d1ecefa59f88d55d9e765f52f75bd9 upstream.

During the code change to add the support for devres-managed card
instance, we put an explicit kfree(card) call at the error path in
snd_card_new(). This is needed for the early error path before the
card is initialized with the device, but is rather superfluous and
causes a double-free at the error path after the card instance is
initialized, as the destructor of the card object already contains a
kfree() call.

This patch fixes the double-free situation by removing the superfluous
kfree(). Meanwhile we need to call kfree() explicitly for the early
error path, so it's added there instead.

Fixes: e8ad415b7a55 ("ALSA: core: Add managed card creation")
Reported-by: Rondreis <linhaoguo86@gmail.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/CAB7eexL1zBnB636hwS27d-LdPYZ_R1-5fJS_h=ZbCWYU=UPWJg@mail.gmail.com
Link: https://lore.kernel.org/r/20220919123516.28222-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
sound/core/init.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

--- a/sound/core/init.c
+++ b/sound/core/init.c
@@ -178,10 +178,8 @@ int snd_card_new(struct device *parent,
return -ENOMEM;

err = snd_card_init(card, parent, idx, xid, module, extra_size);
- if (err < 0) {
- kfree(card);
- return err;
- }
+ if (err < 0)
+ return err; /* card is freed by error handler */

*card_ret = card;
return 0;
@@ -231,7 +229,7 @@ int snd_devm_card_new(struct device *par
card->managed = true;
err = snd_card_init(card, parent, idx, xid, module, extra_size);
if (err < 0) {
- devres_free(card);
+ devres_free(card); /* in managed mode, we need to free manually */
return err;
}

@@ -293,6 +291,8 @@ static int snd_card_init(struct snd_card
mutex_unlock(&snd_card_mutex);
dev_err(parent, "cannot find the slot for index %d (range 0-%i), error: %d\n",
idx, snd_ecards_limit - 1, err);
+ if (!card->managed)
+ kfree(card); /* manually free here, as no destructor called */
return err;
}
set_bit(idx, snd_cards_lock); /* lock it */