usb: typec: bus: verify partner exists in typec_altmode_attention

commit f23643306430f86e2f413ee2b986e0773e79da31 upstream. Some usb hubs will negotiate DisplayPort Alt mode with the device but will then negotiate a data role swap after entering the alt mode. The data role swap causes the device to unregister all alt modes, however the usb hub will still send Attention messages even after failing to reregister the Alt Mode. type_altmode_attention currently does not verify whether or not a device's altmode partner exists, which results in a NULL pointer error when dereferencing the typec_altmode and typec_altmode_ops belonging to the altmode partner. Verify the presence of a device's altmode partner before sending the Attention message to the Alt Mode driver. Fixes: 8a37d87 ("usb: typec: Bus type for alternate modes") Cc: stable@vger.kernel.org Signed-off-by: RD Babiera <rdbabiera@google.com> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com> Reviewed-by: Guenter Roeck <linux@roeck-us.net> Link: https://lore.kernel.org/r/20230814180559.923475-1-rdbabiera@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ljia5 · Sep 19, 2023 · 0ad6bad · 0ad6bad
1 parent 31220bd
commit 0ad6bad
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Showing 3 changed files with 13 additions and 4 deletions.
diff --git a/drivers/usb/typec/bus.c b/drivers/usb/typec/bus.c
@@ -154,12 +154,20 @@ EXPORT_SYMBOL_GPL(typec_altmode_exit);
  *
  * Notifies the partner of @adev about Attention command.
  */
-void typec_altmode_attention(struct typec_altmode *adev, u32 vdo)
+int typec_altmode_attention(struct typec_altmode *adev, u32 vdo)
 {
-	struct typec_altmode *pdev = &to_altmode(adev)->partner->adev;
+	struct altmode *partner = to_altmode(adev)->partner;
+	struct typec_altmode *pdev;
+
+	if (!partner)
+		return -ENODEV;
+
+	pdev = &partner->adev;
 
 	if (pdev->ops && pdev->ops->attention)
 		pdev->ops->attention(pdev, vdo);
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(typec_altmode_attention);
 

diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
@@ -1863,7 +1863,8 @@ static void tcpm_handle_vdm_request(struct tcpm_port *port,
 			}
 			break;
 		case ADEV_ATTENTION:
-			typec_altmode_attention(adev, p[1]);
+			if (typec_altmode_attention(adev, p[1]))
+				tcpm_log(port, "typec_altmode_attention no port partner altmode");
 			break;
 		}
 	}

diff --git a/include/linux/usb/typec_altmode.h b/include/linux/usb/typec_altmode.h
@@ -67,7 +67,7 @@ struct typec_altmode_ops {
 
 int typec_altmode_enter(struct typec_altmode *altmode, u32 *vdo);
 int typec_altmode_exit(struct typec_altmode *altmode);
-void typec_altmode_attention(struct typec_altmode *altmode, u32 vdo);
+int typec_altmode_attention(struct typec_altmode *altmode, u32 vdo);
 int typec_altmode_vdm(struct typec_altmode *altmode,
 		      const u32 header, const u32 *vdo, int count);
 int typec_altmode_notify(struct typec_altmode *altmode, unsigned long conf,