FAILED: patch "[PATCH] ALSA: usb-audio: qcom: Check the return value of qmi_handle_init()" failed to apply to 6.18-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x a3cf5ebab5f1db9e6f751e2a08df05a84f37ea57
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261109200549-failed-6.18-a3cf5ebab5f1@kernel.org' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From a3cf5ebab5f1db9e6f751e2a08df05a84f37ea57 Mon Sep 17 00:00:00 2001
From: Yuqiang Sun <izaiahsun@gmail.com>
Date: Mon, 2 Nov 2026 11:52:37 +0800
Subject: [PATCH] ALSA: usb-audio: qcom: Check the return value of
 qmi_handle_init()

qc_usb_audio_probe() overwrites the return value of qmi_handle_init()
with that of qmi_add_server() without checking it. When
qmi_handle_init() fails, it has already freed the receive buffer and
destroyed the workqueue, and qmi->sock may hold an error pointer. If
QRTR is not available, qmi_handle_init() returns -EPROBE_DEFER and
qmi->sock is ERR_PTR(-EAFNOSUPPORT), so qmi_add_server() passes it to
kernel_sendmsg():

  BUG: unable to handle page fault for address: ffffffffffffffb7
  RIP: 0010:selinux_socket_sendmsg+0xa0/0x590
  Call Trace:
   security_socket_sendmsg+0x29/0x50
   __sock_sendmsg+0x43/0x150
   kernel_sendmsg+0xd6/0x180
   qmi_send_new_server+0x1b8/0x2b0
   qmi_add_server+0x165/0x200
   qc_usb_audio_probe+0xf4/0x2e0
   really_probe+0x2b4/0x850

Had the probe gone on, the error and remove paths would call
qmi_handle_release() on the half-initialized handle, which destroys the
workqueue and frees the receive buffer a second time.

Return the error from qmi_handle_init(), so that -EPROBE_DEFER defers
the probe, and check qmi_add_server() as well.

The bug was found with kbound, a static analysis prototype for
ownership mismatches at kernel interfaces, on v7.2.12; it is present in
mainline.

Build-tested with x86_64 and arm64 allmodconfig (W=1, sparse): no new
warnings. Run-tested on QEMU (x86_64, KVM) with KASAN and kmemleak, with
the driver built in and a test module that registers the
q6usb.qc-usb-audio-offload auxiliary device. Without QRTR, the probe
crashes as above without this patch; with it the device is deferred and
removing it again reports nothing. With QRTR the probe succeeds, and
removal reports nothing either.

Fixes: 326bbc348298 ("ALSA: usb-audio: qcom: Introduce QC USB SND offloading support")
Cc: stable@vger.kernel.org
Signed-off-by: Yuqiang Sun <izaiahsun@gmail.com>
Link: https://patch.msgid.link/20261102035237.56253-1-izaiahsun@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 sound/usb/qcom/qc_audio_offload.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/sound/usb/qcom/qc_audio_offload.c b/sound/usb/qcom/qc_audio_offload.c
index e4bfd43a2488b..5ee568e0454cb 100644
--- a/sound/usb/qcom/qc_audio_offload.c
+++ b/sound/usb/qcom/qc_audio_offload.c
@@ -1969,8 +1969,13 @@ static int qc_usb_audio_probe(struct auxiliary_device *auxdev,
 			      QMI_UAUDIO_STREAM_REQ_MSG_V01_MAX_MSG_LEN,
 			      &uaudio_svc_ops_options,
 			      &uaudio_stream_req_handlers);
+	if (ret)
+		goto free_qmi_hdl;
+
 	ret = qmi_add_server(svc->uaudio_svc_hdl, UAUDIO_STREAM_SERVICE_ID_V01,
 			     UAUDIO_STREAM_SERVICE_VERS_V01, 0);
+	if (ret)
+		goto release_qmi_hdl;
 
 	uaudio_svc = svc;
 
@@ -1987,7 +1992,9 @@ static int qc_usb_audio_probe(struct auxiliary_device *auxdev,
 
 release_qmi:
 	qc_usb_audio_cleanup_qmi_dev();
+release_qmi_hdl:
 	qmi_handle_release(svc->uaudio_svc_hdl);
+free_qmi_hdl:
 	kfree(svc->uaudio_svc_hdl);
 free_svc:
 	kfree(svc);
-- 
2.53.0