usb: typec: ucsi: Retrieve all the PDOs instead of just the first 4

commit 4dbc6a4e ("usb: typec: ucsi: save power data objects
in PD mode") introduced retrieval of the PDOs when connected to a
PD-capable source. But only the first 4 PDOs are received since
that is the maximum number that can be fetched at a time given the
MESSAGE_IN length limitation (16 bytes). However, as per the PD spec
a connected source may advertise up to a maximum of 7 PDOs.

If such a source is connected it's possible the PPM could have
negotiated a power contract with one of the PDOs at index greater
than 4, and would be reflected in the request data object's (RDO)
object position field. This would result in an out-of-bounds access
when the rdo_index() is used to index into the src_pdos array in
ucsi_psy_get_voltage_now().

With the help of the UBSAN -fsanitize=array-bounds checker enabled
this exact issue is revealed when connecting to a PD source adapter
that advertise 5 PDOs and the PPM enters a contract having selected
the 5th one.

[  151.545106][   T70] Unexpected kernel BRK exception at EL1
[  151.545112][   T70] Internal error: BRK handler: f2005512 [#1] PREEMPT SMP
...
[  151.545499][   T70] pc : ucsi_psy_get_prop+0x208/0x20c
[  151.545507][   T70] lr : power_supply_show_property+0xc0/0x328
...
[  151.545542][   T70] Call trace:
[  151.545544][   T70]  ucsi_psy_get_prop+0x208/0x20c
[  151.545546][   T70]  power_supply_uevent+0x1a4/0x2f0
[  151.545550][   T70]  dev_uevent+0x200/0x384
[  151.545555][   T70]  kobject_uevent_env+0x1d4/0x7e8
[  151.545557][   T70]  power_supply_changed_work+0x174/0x31c
[  151.545562][   T70]  process_one_work+0x244/0x6f0
[  151.545564][   T70]  worker_thread+0x3e0/0xa64

We can resolve this by instead retrieving and storing up to the
maximum of 7 PDOs in the con->src_pdos array. This would involve
two calls to the GET_PDOS command.

Fixes: 992a60ed ("usb: typec: ucsi: register with power_supply class")
Fixes: 4dbc6a4e ("usb: typec: ucsi: save power data objects in PD mode")
Cc: stable@vger.kernel.org
Reported-and-tested-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Link: https://lore.kernel.org/r/20210503074611.30973-1-jackp@codeaurora.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/ucsi/ucsi.c

@@ -495,7 +495,8 @@ static void ucsi_unregister_altmodes(struct ucsi_connector *con, u8 recipient)
 	}
 }
 
-static void ucsi_get_pdos(struct ucsi_connector *con, int is_partner)
+static int ucsi_get_pdos(struct ucsi_connector *con, int is_partner,
+			 u32 *pdos, int offset, int num_pdos)
 {
 	struct ucsi *ucsi = con->ucsi;
 	u64 command;
@@ -503,17 +504,39 @@ static void ucsi_get_pdos(struct ucsi_connector *con, int is_partner)
 
 	command = UCSI_COMMAND(UCSI_GET_PDOS) | UCSI_CONNECTOR_NUMBER(con->num);
 	command |= UCSI_GET_PDOS_PARTNER_PDO(is_partner);
-	command |= UCSI_GET_PDOS_NUM_PDOS(UCSI_MAX_PDOS - 1);
+	command |= UCSI_GET_PDOS_PDO_OFFSET(offset);
+	command |= UCSI_GET_PDOS_NUM_PDOS(num_pdos - 1);
 	command |= UCSI_GET_PDOS_SRC_PDOS;
-	ret = ucsi_send_command(ucsi, command, con->src_pdos,
-			       sizeof(con->src_pdos));
-	if (ret < 0) {
+	ret = ucsi_send_command(ucsi, command, pdos + offset,
+				num_pdos * sizeof(u32));
+	if (ret < 0)
 		dev_err(ucsi->dev, "UCSI_GET_PDOS failed (%d)\n", ret);
+	if (ret == 0 && offset == 0)
+		dev_warn(ucsi->dev, "UCSI_GET_PDOS returned 0 bytes\n");
+
+	return ret;
+}
+
+static void ucsi_get_src_pdos(struct ucsi_connector *con, int is_partner)
+{
+	int ret;
+
+	/* UCSI max payload means only getting at most 4 PDOs at a time */
+	ret = ucsi_get_pdos(con, 1, con->src_pdos, 0, UCSI_MAX_PDOS);
+	if (ret < 0)
 		return;
-	}
+
 	con->num_pdos = ret / sizeof(u32); /* number of bytes to 32-bit PDOs */
-	if (ret == 0)
-		dev_warn(ucsi->dev, "UCSI_GET_PDOS returned 0 bytes\n");
+	if (con->num_pdos < UCSI_MAX_PDOS)
+		return;
+
+	/* get the remaining PDOs, if any */
+	ret = ucsi_get_pdos(con, 1, con->src_pdos, UCSI_MAX_PDOS,
+			    PDO_MAX_OBJECTS - UCSI_MAX_PDOS);
+	if (ret < 0)
+		return;
+
+	con->num_pdos += ret / sizeof(u32);
 }
 
 static void ucsi_pwr_opmode_change(struct ucsi_connector *con)
@@ -522,7 +545,7 @@ static void ucsi_pwr_opmode_change(struct ucsi_connector *con)
 	case UCSI_CONSTAT_PWR_OPMODE_PD:
 		con->rdo = con->status.request_data_obj;
 		typec_set_pwr_opmode(con->port, TYPEC_PWR_MODE_PD);
-		ucsi_get_pdos(con, 1);
+		ucsi_get_src_pdos(con, 1);
 		break;
 	case UCSI_CONSTAT_PWR_OPMODE_TYPEC1_5:
 		con->rdo = 0;

drivers/usb/typec/ucsi/ucsi.h

@@ -8,6 +8,7 @@
 #include <linux/power_supply.h>
 #include <linux/types.h>
 #include <linux/usb/typec.h>
+#include <linux/usb/pd.h>
 #include <linux/usb/role.h>
 
 /* -------------------------------------------------------------------------- */
@@ -134,7 +135,9 @@ void ucsi_connector_change(struct ucsi *ucsi, u8 num);
 
 /* GET_PDOS command bits */
 #define UCSI_GET_PDOS_PARTNER_PDO(_r_)		((u64)(_r_) << 23)
+#define UCSI_GET_PDOS_PDO_OFFSET(_r_)		((u64)(_r_) << 24)
 #define UCSI_GET_PDOS_NUM_PDOS(_r_)		((u64)(_r_) << 32)
+#define UCSI_MAX_PDOS				(4)
 #define UCSI_GET_PDOS_SRC_PDOS			((u64)1 << 34)
 
 /* -------------------------------------------------------------------------- */
@@ -302,7 +305,6 @@ struct ucsi {
 
 #define UCSI_MAX_SVID		5
 #define UCSI_MAX_ALTMODES	(UCSI_MAX_SVID * 6)
-#define UCSI_MAX_PDOS		(4)
 
 #define UCSI_TYPEC_VSAFE5V	5000
 #define UCSI_TYPEC_1_5_CURRENT	1500
@@ -330,7 +332,7 @@ struct ucsi_connector {
 	struct power_supply *psy;
 	struct power_supply_desc psy_desc;
 	u32 rdo;
-	u32 src_pdos[UCSI_MAX_PDOS];
+	u32 src_pdos[PDO_MAX_OBJECTS];
 	int num_pdos;
 
 	struct usb_role_switch *usb_role_sw;