Re: [PATCH v2] usb: storage: ene_ub6250: set transport_reset to avoid NULL deref

[Alan Stern]

On Thu, Sep 10, 2026 at 12:19:26AM +0700, Nguyen Ngoc Thang wrote:
> ene_ub6250_probe() sets us->transport but never sets
> us->transport_reset. get_transport() only fills in transport_reset
> for the standard USB_PR_CB/CBI/BULK protocols; since this driver
> matches on VID/PID alone, a device can report any bInterfaceProtocol
> value and still bind, leaving transport_reset NULL.
> 
> When the transport then reports an error, usb_stor_invoke_transport()
> calls us->transport_reset(us) in its Handle_Errors path, dereferencing
> a NULL function pointer:
> 
>   BUG: kernel NULL pointer dereference, address: 0000000000000000
>   RIP: 0010:0x0
>   Call Trace:
>    usb_stor_invoke_transport+0x55a/0x1a40 drivers/usb/storage/transport.c:926
>    usb_stor_control_thread+0x44c/0x8f0 drivers/usb/storage/usb.c:462
>    kthread+0x38b/0x480 kernel/kthread.c:436
> 
> Set transport_reset to usb_stor_Bulk_reset: ene_send_scsi_cmd()
> already frames its command/status packets with the shared
> struct bulk_cb_wrap/bulk_cs_wrap from include/linux/usb/storage.h
> and only ever transfers over us->send_bulk_pipe/recv_bulk_pipe, i.e.
> this device speaks the Bulk-Only Transport wire protocol underneath
> its own SCSI translation layer, so the Bulk-Only reset is the correct
> recovery action for it, matching the pattern already used by the
> other subdrivers with a custom transport function (alauda, datafab,
> jumpshot, karma).
> 
> Also harden usb_stor_probe2()'s existing sanity check to require
> transport_reset alongside transport and proto_handler, so a future
> subdriver making the same mistake fails to probe instead of crashing
> on the first error recovery.
> 
> Reported-by: syzbot+356ae236154297f0d60d@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=356ae236154297f0d60d
> Signed-off-by: Nguyen Ngoc Thang <ngocthang2710.1999@xxxxxxxxx>
> ---
> v2: per Alan Stern's review, justify why usb_stor_Bulk_reset is the
>     correct choice for ene_ub6250, and additionally harden
>     usb_stor_probe2()'s NULL check to cover transport_reset so other
>     subdrivers can't hit the same bug.

Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>

>  drivers/usb/storage/ene_ub6250.c | 2 ++
>  drivers/usb/storage/usb.c        | 6 ++++--
>  2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/storage/ene_ub6250.c b/drivers/usb/storage/ene_ub6250.c
> index ed49a3bc859c..3137c2cdd021 100644
> --- a/drivers/usb/storage/ene_ub6250.c
> +++ b/drivers/usb/storage/ene_ub6250.c
> @@ -2350,6 +2350,8 @@ static int ene_ub6250_probe(struct usb_interface *intf,
> 
>  	us->transport_name = "ene_ub6250";
>  	us->transport = ene_transport;
> +	/* get_transport() only sets this for the standard USB_PR_* protocols */
> +	us->transport_reset = usb_stor_Bulk_reset;
>  	us->max_lun = 0;
> 
>  	result = usb_stor_probe2(us);
> diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c
> index 064c7fc8e368..823a4b2e9033 100644
> --- a/drivers/usb/storage/usb.c
> +++ b/drivers/usb/storage/usb.c
> @@ -1100,8 +1100,10 @@ int usb_stor_probe2(struct us_data *us)
>  	int result;
>  	struct device *dev = &us->pusb_intf->dev;
> 
> -	/* Make sure the transport and protocol have both been set */
> -	if (!us->transport || !us->proto_handler) {
> +	/* Make sure the transport, its reset method, and the protocol
> +	 * have all been set
> +	 */
> +	if (!us->transport || !us->transport_reset || !us->proto_handler) {
>  		result = -ENXIO;
>  		goto BadDevice;
>  	}
> --
> 2.43.0