linux-kernel - [PATCH] [RFC PATCH] ALSA: usb-audio: endpoint: Prevent NULL pointer deference in snd_usb_endpoint

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Date: Fri, 26 Apr 2024 17:55:11 +0530
From: Rajashekar kuruva <quic_kuruva@...cinc.com>
To: <srinivas.kandagatla@...aro.org>, <mathias.nyman@...el.com>,
        <perex@...ex.cz>, <conor+dt@...nel.org>, <corbet@....net>,
        <lgirdwood@...il.com>, <andersson@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <gregkh@...uxfoundation.org>,
        <Thinh.Nguyen@...opsys.com>, <broonie@...nel.org>,
        <bgoswami@...cinc.com>, <tiwai@...e.com>, <robh@...nel.org>,
        <konrad.dybcio@...aro.org>
CC: <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-sound@...r.kernel.org>, <linux-usb@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <alsa-devel@...a-project.org>,
        Rajashekar kuruva <quic_kuruva@...cinc.com>
Subject: [PATCH] [RFC PATCH] ALSA: usb-audio: endpoint: Prevent NULL pointer deference in snd_usb_endpoint_close

When multiple plug-in and plug-out events occur,
there is a risk of encountering a NULL pointer dereference
leading to a kernel panic during a headset use-case.
this issue arises in the snd_usb_endpoint_close function

To avoid check if ep->iface_ref is not null before decrementing
its opened count. If ep->iface_ref is null, we skip the decrement
and the subsequent logic.

Signed-off-by: Rajashekar kuruva <quic_kuruva@...cinc.com>
---
 sound/usb/endpoint.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 8f65349a06d3..0e3101b7e392 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -950,7 +950,7 @@ void snd_usb_endpoint_close(struct snd_usb_audio *chip,
 	usb_audio_dbg(chip, "Closing EP 0x%x (count %d)\n",
 		      ep->ep_num, ep->opened);
 
-	if (!--ep->iface_ref->opened &&
+	if (ep->iface_ref && !--ep->iface_ref->opened &&
 		!(chip->quirk_flags & QUIRK_FLAG_IFACE_SKIP_CLOSE))
 		endpoint_set_interface(chip, ep, false);
 
-- 
2.25.1