linux-kernel - [PATCH 4.9 173/207] ALSA: gus: fix null pointer dereference on pointer block

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Message-Id: <20211124115709.589560565@linuxfoundation.org>
Date:   Wed, 24 Nov 2021 12:57:24 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Chengfeng Ye <cyeaa@...nect.ust.hk>,
        Takashi Iwai <tiwai@...e.de>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 173/207] ALSA: gus: fix null pointer dereference on pointer block

From: Chengfeng Ye <cyeaa@...nect.ust.hk>

[ 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@...nect.ust.hk>
Link: https://lore.kernel.org/r/20211024104611.9919-1-cyeaa@connect.ust.hk
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 sound/isa/gus/gus_dma.c | 2 ++
 1 file changed, 2 insertions(+)

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
-- 
2.33.0