[alsa-devel] Make snd_card_free() a no-op again for NULL ptr argument
Hello Takashi,
Commit “ALSA: Use standard device refcount for card accounting” https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/sound/core/init.c?h=v4.12-rc6&id=f24640648186b59bd39f8cd640d631bdb61a3197 changed the behaviour of snd_card_free() in case of a NULL ptr argument. Before f24640648186b59bd39f8cd640d631bdb61a3197 snd_card_free() was a no-op in case of a NULL ptr argument as I would expect for a *_free() function. Currently passing a NULL ptr results in a NULL ptr dereference.
I believe the previous behaviour is worth restoring. If you agree I’ll follow up with a patch.
Thank you. — Delio
On Thu, 29 Jun 2017 12:46:33 +0200, Delio Brignoli wrote:
Hello Takashi,
Commit “ALSA: Use standard device refcount for card accounting” https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/sound/core/init.c?h=v4.12-rc6&id=f24640648186b59bd39f8cd640d631bdb61a3197 changed the behaviour of snd_card_free() in case of a NULL ptr argument. Before f24640648186b59bd39f8cd640d631bdb61a3197 snd_card_free() was a no-op in case of a NULL ptr argument as I would expect for a *_free() function. Currently passing a NULL ptr results in a NULL ptr dereference.
I believe the previous behaviour is worth restoring. If you agree I’ll follow up with a patch.
In which situation do you need to pass NULL to snd_card_free()?
thanks,
Takashi
On 29 Jun 2017, at 12:49, Takashi Iwai tiwai@suse.de wrote:
On Thu, 29 Jun 2017 12:46:33 +0200, Delio Brignoli wrote:
Hello Takashi,
Commit “ALSA: Use standard device refcount for card accounting” https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/sound/core/init.c?h=v4.12-rc6&id=f24640648186b59bd39f8cd640d631bdb61a3197 changed the behaviour of snd_card_free() in case of a NULL ptr argument. Before f24640648186b59bd39f8cd640d631bdb61a3197 snd_card_free() was a no-op in case of a NULL ptr argument as I would expect for a *_free() function. Currently passing a NULL ptr results in a NULL ptr dereference.
I believe the previous behaviour is worth restoring. If you agree I’ll follow up with a patch.
In which situation do you need to pass NULL to snd_card_free()?
Unconditional calls to snd_card_free(), similarly to unconditional calls to free().
struct snd_card *card = NULL; … /* setup code */ if (something_goes_wrong) goto cleanup; … retval = snd_card_new(…, &card); … cleanup: snd_card_free(card); ...
Sure, code can be re-organized to avoid it but *_free() function being a no-op in case of NULL ptr argument is the norm AFAIK. If so then why snd_card_free() should be different especially if it was doing the "right" thing before.
Thank you -- Delio
participants (2)
-
Delio Brignoli -
Takashi Iwai