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

[Nguyen Ngoc Thang]

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.

 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