Re: [PATCH] ALSA: usb-audio: qcom: Check the return value of qmi_handle_init()

[Takashi Iwai <tiwai@suse.de>]

On Mon, 02 Nov 2026 04:52:37 +0100,
Yuqiang Sun wrote:
> 
> 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>

Applied now.  Thanks.


Takashi