[PATCH v3 2/2] usb: typec: tipd: fix uninitialized typec_partner_desc in cd321x_update_work()

cd321x_update_work() passes a stack-allocated typec_partner_desc to
typec_register_partner() after initializing only usb_pd, accessory and
identity.

typec_register_partner() copies attach and deattach from the descriptor
into the partner. With those fields left unset, garbage function pointers
may be stored and later invoked from typec_partner_link_device() when a USB
device is linked to the port. Uninitialized pd_revision and usb_capability
similarly leak stack data through partner sysfs.

Zero-initialize the descriptor so optional callbacks remain NULL and the
remaining fields are zero.

Fixes: 82432bbfb9e8 ("usb: typec: tipd: Handle mode transitions for CD321x")
Cc: [email protected] # 6.18+
Signed-off-by: Radhey Shyam Pandey <[email protected]>
---
Changes for v3:
- Split v2 into separate patches to simplify LTS backporting.
- Drop Heikki reviewed-by tag as now patch is split.

Changes for v2:
- Add  Assisted-by tag.
- Remove explicit indentity=NULL

AI code scanning identified this issue; the possible call graph is shown below.

  USB-C plug event (IRQ)
    tps6598x_interrupt()
      tps6598x_handle_plug_event()
        tps6598x_connect()
          struct typec_partner_desc desc;     /* bug: attach/deattach unset */
          desc.usb_pd / .accessory / .identity = ...
          typec_register_partner(port, &desc)   /* class.c */
            partner->attach   = desc->attach;   /* copy stack garbage */
            partner->deattach = desc->deattach;
            [if port->usb2_dev || port->usb3_dev already set]
              typec_partner_link_device(partner, dev)
                if (partner->attach)
                  partner->attach(partner, dev)  /* indirect call via bad ptr */
---
 drivers/usb/typec/tipd/core.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/usb/typec/tipd/core.c b/drivers/usb/typec/tipd/core.c
index 54ca726c3b15..d99a55063e34 100644
--- a/drivers/usb/typec/tipd/core.c
+++ b/drivers/usb/typec/tipd/core.c
@@ -840,11 +840,10 @@ static void cd321x_update_work(struct work_struct *work)
 
 	/* Set up partner if we were previously disconnected (or changed). */
 	if (!tps->partner) {
-		struct typec_partner_desc desc;
+		struct typec_partner_desc desc = { };
 
 		desc.usb_pd = is_pd;
 		desc.accessory = TYPEC_ACCESSORY_NONE; /* XXX: handle accessories */
-		desc.identity = NULL;
 
 		if (desc.usb_pd)
 			desc.identity = &st.partner_identity;
-- 
2.43.0