ALSA: core: Fix double-free at snd_card_new()

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>

diff --git a/sound/core/init.c b/sound/core/init.c
index 193dae3..5377f94 100644 (file)
--- a/sound/core/init.c
+++ b/sound/core/init.c
@@ -178,10 +178,8 @@ int snd_card_new(struct device *parent, int idx, const char *xid,
                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;
@@ -233,7 +231,7 @@ int snd_devm_card_new(struct device *parent, int idx, const char *xid,
        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;
        }
 
@@ -297,6 +295,8 @@ static int snd_card_init(struct snd_card *card, struct device *parent,
                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 */