linux-kernel - [PATCH] ALSA: usb-audio: qcom: fix NULL pointer dereference in qmi_stop

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Message-Id: <9da1a13ffee0924e4813ef5b20625a89680ce88d.1750745062.git.xiaopei01@kylinos.cn>
Date: Tue, 24 Jun 2025 14:06:06 +0800
From: Pei Xiao <xiaopei01@...inos.cn>
To: tiwai@...e.com,
	perex@...ex.cz,
	quic_wcheng@...cinc.com,
	linux-sound@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Pei Xiao <xiaopei01@...inos.cn>
Subject: [PATCH] ALSA: usb-audio: qcom: fix NULL pointer dereference in qmi_stop_session

The find_substream() call may return NULL, but the original error path
dereferenced 'subs' unconditionally in dev_err(&subs->dev->dev, ...),
causing a NULL pointer dereference when subs is NULL.

Fix by replacing dev_err with pr_err which doesn't require device context.
This safely handles NULL subs while preserving the critical debugging
information (pcm_card_num, pcm_dev_num, direction).

Signed-off-by: Pei Xiao <xiaopei01@...inos.cn>
---
 sound/usb/qcom/qc_audio_offload.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/sound/usb/qcom/qc_audio_offload.c b/sound/usb/qcom/qc_audio_offload.c
index 5bc27c82e0af..556fd9cb4fa6 100644
--- a/sound/usb/qcom/qc_audio_offload.c
+++ b/sound/usb/qcom/qc_audio_offload.c
@@ -759,8 +759,7 @@ static void qmi_stop_session(void)
 			subs = find_substream(pcm_card_num, info->pcm_dev_num,
 					      info->direction);
 			if (!subs || !chip || atomic_read(&chip->shutdown)) {
-				dev_err(&subs->dev->dev,
-					"no sub for c#%u dev#%u dir%u\n",
+				pr_err("no sub for c#%u dev#%u dir%u\n",
 					info->pcm_card_num,
 					info->pcm_dev_num,
 					info->direction);
-- 
2.25.1