[PATCH 5.4 151/158] ALSA: pcm: Check for null pointer of pointer substream before dereferencing it

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5.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Colin Ian King <colin.i.king@xxxxxxxxx>

commit 011b559be832194f992f73d6c0d5485f5925a10b upstream.

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@xxxxxxxxx>
Link: https://lore.kernel.org/r/20220424205945.1372247-1-colin.i.king@xxxxxxxxx
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 sound/core/pcm_memory.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/sound/core/pcm_memory.c
+++ b/sound/core/pcm_memory.c
@@ -401,7 +401,6 @@ 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))
@@ -410,6 +409,8 @@ int snd_pcm_lib_free_pages(struct snd_pc
 	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);





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