ALSA: pcm: Check for null pointer of pointer substream before dereferencing it

[ Upstream commit 011b559be832194f992f73d6c0d5485f5925a10b ]

Pointer substream is being dereferenced on the assignment of pointer card
before substream is being null checked with the macro PCM_RUNTIME_CHECK.
Although PCM_RUNTIME_CHECK calls BUG_ON, it still is useful to perform the
the pointer check before card is assigned.

Fixes: d4cfb30fce03 ("ALSA: pcm: Set per-card upper limit of PCM buffer allocations")
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20220424205945.1372247-1-colin.i.king@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/sound/core/pcm_memory.c b/sound/core/pcm_memory.c
index f1fb856..f147059 100644 (file)
--- a/sound/core/pcm_memory.c
+++ b/sound/core/pcm_memory.c
@@ -446,7 +446,6 @@ EXPORT_SYMBOL(snd_pcm_lib_malloc_pages);
  */
 int snd_pcm_lib_free_pages(struct snd_pcm_substream *substream)
 {
-       struct snd_card *card = substream->pcm->card;
        struct snd_pcm_runtime *runtime;
 
        if (PCM_RUNTIME_CHECK(substream))
@@ -455,6 +454,8 @@ int snd_pcm_lib_free_pages(struct snd_pcm_substream *substream)
        if (runtime->dma_area == NULL)
                return 0;
        if (runtime->dma_buffer_p != &substream->dma_buffer) {
+               struct snd_card *card = substream->pcm->card;
+
                /* it's a newly allocated buffer.  release it now. */
                do_free_pages(card, runtime->dma_buffer_p);
                kfree(runtime->dma_buffer_p);