Re: [alsa-devel] [RFC PATCH v2] ASoC: dpcm: prevent snd_soc_dpcm use after free

On Wed, Mar 06, 2019 at 10:19:38AM +0100, Jaroslav Kysela wrote:

Dne 06. 03. 19 v 9:46 KaiChieh Chuang napsal(a):

...

• spin_lock(&fe->card->dpcm_lock);
  

  list_del(&dpcm->list_be); list_del(&dpcm->list_fe); kfree(dpcm);

• spin_unlock(&fe->card->dpcm_lock);
  

The unlock might be moved before kfree(). Also, I don't see the list_add() spin lock protection in your patch.

Yes, the free *needs* to be outside of the spinlocked section - we shouldn't do dynamic memory operations in atomics context.