Re: [PATCH RFC] usb: atm: cxacru: properly kill rcv_urb on error in cxacru_cm()

#syz upstream

On Fri, Jul 31, 2026 at 9:54=E2=80=AFAM 'syzbot' via
syzkaller-upstream-moderation
<[email protected]> wrote:
>
> If cxacru_cm() encounters an error while submitting or waiting for snd_ur=
b,
> it aborts and returns the error without killing the already submitted
> rcv_urb. This leaves the rcv_urb active.
>
> When this happens during initialization (e.g., in cxacru_atm_start()), th=
e
> driver may ignore the error and proceed to call cxacru_poll_status(), whi=
ch
> invokes cxacru_cm() again. Attempting to submit the still-active rcv_urb
> triggers a warning in usb_submit_urb():
>
> cxacru 1-1:1.0: send of cm 0x84 failed (-104)
> ATM dev 0: cxacru_atm_start: CHIP_ADSL_LINE_START returned -104
> ------------[ cut here ]------------
> URB ffff88812658d200 submitted while active
> WARNING: drivers/usb/core/urb.c:379 at usb_submit_urb+0x79/0x18b0
> drivers/usb/core/urb.c:379
> ...
> Call Trace:
>  <TASK>
>  cxacru_cm+0x21a/0xf10 drivers/usb/atm/cxacru.c:631
>  cxacru_cm_get_array drivers/usb/atm/cxacru.c:722 [inline]
>  cxacru_poll_status+0x178/0x1110 drivers/usb/atm/cxacru.c:828
>  cxacru_atm_start+0x185/0x360 drivers/usb/atm/cxacru.c:814
>  usbatm_atm_init+0x144/0x3a0 drivers/usb/atm/usbatm.c:927
>  usbatm_usb_probe+0x15cb/0x1db0 drivers/usb/atm/usbatm.c:1178
>  cxacru_usb_probe+0x17f/0x220 drivers/usb/atm/cxacru.c:1370
> ...
>
> To fix this, ensure that rcv_urb is properly killed if cxacru_cm() aborts
> early. We can safely call usb_kill_urb() on rcv_urb in the error path, as
> it is safe to call even if the URB is not active (e.g., if it failed to
> submit in the first place, or if it already completed).
>
> Fixes: 1b0e61465234 ("[PATCH] USB ATM: driver for the Conexant AccessRunn=
er chipset cxacru")
> Assisted-by: Gemini:gemini-3.5-flash Gemini:gemini-3.1-pro-preview syzbot
> Reported-by: [email protected]
> Closes: https://syzkaller.appspot.com/bug?extid=3Dc9dff578c3a41775176a
> Link: https://syzkaller.appspot.com/ai_job?id=3D75fec6f2-c8a6-43b1-b184-4=
d26baba86cc
> To: "Chas Williams" <[email protected]>
> To: <[email protected]>
> To: "Greg Kroah-Hartman" <[email protected]>
> To: <[email protected]>
> To: <[email protected]>
> To: <[email protected]>
> To: "Duncan Sands" <[email protected]>
> Cc: <[email protected]>
>
> ---
> diff --git a/drivers/usb/atm/cxacru.c b/drivers/usb/atm/cxacru.c
> index f1900c567..429ac20a8 100644
> --- a/drivers/usb/atm/cxacru.c
> +++ b/drivers/usb/atm/cxacru.c
> @@ -700,6 +700,8 @@ static int cxacru_cm(struct cxacru_data *instance, en=
um cxacru_cm_request cm,
>         ret =3D offd;
>         usb_dbg(instance->usbatm, "cm %#x\n", cm);
>  fail:
> +       if (ret < 0)
> +               usb_kill_urb(instance->rcv_urb);
>         mutex_unlock(&instance->cm_serialize);
>  err:
>         return ret;
>
>
> base-commit: f5098b6bae761e346ebcd9da7f95622c04733cff
> --
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