[PATCH v2] usb: typec: tcpm: Check for port partner validity before consuming it

[Badhri Jagan Sridharan <badhri@xxxxxxxxxx>]

typec_register_partner() does not guarantee partner registration
to always succeed. In the event of failure, port->partner is set
to the error value or NULL. Given that port->partner validity is
not checked, this results in the following crash:

Unable to handle kernel NULL pointer dereference at virtual address 00000000000003c0
 pc : run_state_machine+0x1bc8/0x1c08
 lr : run_state_machine+0x1b90/0x1c08
..
 Call trace:
   run_state_machine+0x1bc8/0x1c08
   tcpm_state_machine_work+0x94/0xe4
   kthread_worker_fn+0x118/0x328
   kthread+0x1d0/0x23c
   ret_from_fork+0x10/0x20

To prevent the crash, check for port->partner validity before
derefencing it in all the call sites.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: c97cd0b4b54e ("usb: typec: tcpm: set initial svdm version based on pd revision")
Signed-off-by: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
---
 drivers/usb/typec/tcpm/tcpm.c | 31 +++++++++++++++++++++++--------
 1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index ab6ed6111ed0..454165776797 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -4,7 +4,6 @@
  *
  * USB Power Delivery protocol stack.
  */
-
 #include <linux/completion.h>
 #include <linux/debugfs.h>
 #include <linux/device.h>
@@ -1580,7 +1579,8 @@ static void svdm_consume_identity(struct tcpm_port *port, const u32 *p, int cnt)
 	port->partner_ident.cert_stat = p[VDO_INDEX_CSTAT];
 	port->partner_ident.product = product;
 
-	typec_partner_set_identity(port->partner);
+	if (port->partner)
+		typec_partner_set_identity(port->partner);
 
 	tcpm_log(port, "Identity: %04x:%04x.%04x",
 		 PD_IDH_VID(vdo),
@@ -1742,6 +1742,9 @@ static void tcpm_register_partner_altmodes(struct tcpm_port *port)
 	struct typec_altmode *altmode;
 	int i;
 
+	if (!port->partner)
+		return;
+
 	for (i = 0; i < modep->altmodes; i++) {
 		altmode = typec_partner_register_altmode(port->partner,
 						&modep->altmode_desc[i]);
@@ -4231,7 +4234,10 @@ static int tcpm_init_vconn(struct tcpm_port *port)
 
 static void tcpm_typec_connect(struct tcpm_port *port)
 {
+	struct typec_partner *partner;
+
 	if (!port->connected) {
+		port->connected = true;
 		/* Make sure we don't report stale identity information */
 		memset(&port->partner_ident, 0, sizeof(port->partner_ident));
 		port->partner_desc.usb_pd = port->pd_capable;
@@ -4241,9 +4247,13 @@ static void tcpm_typec_connect(struct tcpm_port *port)
 			port->partner_desc.accessory = TYPEC_ACCESSORY_AUDIO;
 		else
 			port->partner_desc.accessory = TYPEC_ACCESSORY_NONE;
-		port->partner = typec_register_partner(port->typec_port,
-						       &port->partner_desc);
-		port->connected = true;
+		partner = typec_register_partner(port->typec_port, &port->partner_desc);
+		if (IS_ERR(partner)) {
+			dev_err(port->dev, "Failed to register partner (%ld)\n", PTR_ERR(partner));
+			return;
+		}
+
+		port->partner = partner;
 		typec_partner_set_usb_power_delivery(port->partner, port->partner_pd);
 	}
 }
@@ -4323,9 +4333,11 @@ static void tcpm_typec_disconnect(struct tcpm_port *port)
 	port->plug_prime = NULL;
 	port->cable = NULL;
 	if (port->connected) {
-		typec_partner_set_usb_power_delivery(port->partner, NULL);
-		typec_unregister_partner(port->partner);
-		port->partner = NULL;
+		if (port->partner) {
+			typec_partner_set_usb_power_delivery(port->partner, NULL);
+			typec_unregister_partner(port->partner);
+			port->partner = NULL;
+		}
 		port->connected = false;
 	}
 }
@@ -4549,6 +4561,9 @@ static enum typec_cc_status tcpm_pwr_opmode_to_rp(enum typec_pwr_opmode opmode)
 
 static void tcpm_set_initial_svdm_version(struct tcpm_port *port)
 {
+	if (!port->partner)
+		return;
+
 	switch (port->negotiated_rev) {
 	case PD_REV30:
 		break;

base-commit: 3f12222a4bebeb13ce06ddecc1610ad32fa835dd
-- 
2.44.0.769.g3c40516874-goog