From: Chengfeng Ye <cyeaa@connect.ust.hk>
Date: Sun, 24 Oct 2021 10:46:11 +0000 (-0700)
Subject: ALSA: gus: fix null pointer dereference on pointer block
X-Git-Tag: v4.4.293~34
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3e28e083dcdf03a18a083f8a47b6bb6b1604b5be;p=thirdparty%2Fkernel%2Fstable.git

ALSA: gus: fix null pointer dereference on pointer block

[ Upstream commit a0d21bb3279476c777434c40d969ea88ca64f9aa ]

The pointer block return from snd_gf1_dma_next_block could be
null, so there is a potential null pointer dereference issue.
Fix this by adding a null check before dereference.

Signed-off-by: Chengfeng Ye <cyeaa@connect.ust.hk>
Link: https://lore.kernel.org/r/20211024104611.9919-1-cyeaa@connect.ust.hk
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/sound/isa/gus/gus_dma.c b/sound/isa/gus/gus_dma.c
index 36c27c8323601..2e27cd3427c87 100644
--- a/sound/isa/gus/gus_dma.c
+++ b/sound/isa/gus/gus_dma.c
@@ -141,6 +141,8 @@ static void snd_gf1_dma_interrupt(struct snd_gus_card * gus)
 	}
 	block = snd_gf1_dma_next_block(gus);
 	spin_unlock(&gus->dma_lock);
+	if (!block)
+		return;
 	snd_gf1_dma_program(gus, block->addr, block->buf_addr, block->count, (unsigned short) block->cmd);
 	kfree(block);
 #if 0