Sometimes the embedded controller firmware does not terminate the list of alternate modes that the partner supports in its response to the GET_ALTERNATE_MODES command. Instead the firmware returns the supported alternate modes over and over again until the driver stops requesting them.
If that happens, the number of modes for each alternate mode will exceed the maximum 6 that is defined in the USB Power Delivery specification. Making sure that can't happen by adding a check for it.
This fixes NULL pointer dereference that is caused by the overrun.
Fixes: ad74b8649beaf ("usb: typec: ucsi: Preliminary support for alternate modes") Cc: stable@vger.kernel.org Reported-by: Zwane Mwaikambo zwanem@gmail.com Signed-off-by: Heikki Krogerus heikki.krogerus@linux.intel.com --- drivers/usb/typec/ucsi/ucsi.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-)
diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c index e680fcfdee609..758b988ac518a 100644 --- a/drivers/usb/typec/ucsi/ucsi.c +++ b/drivers/usb/typec/ucsi/ucsi.c @@ -216,14 +216,18 @@ void ucsi_altmode_update_active(struct ucsi_connector *con) con->partner_altmode[i] == altmode); }
-static u8 ucsi_altmode_next_mode(struct typec_altmode **alt, u16 svid) +static int ucsi_altmode_next_mode(struct typec_altmode **alt, u16 svid) { u8 mode = 1; int i;
- for (i = 0; alt[i]; i++) + for (i = 0; alt[i]; i++) { + if (i > MODE_DISCOVERY_MAX) + return -ERANGE; + if (alt[i]->svid == svid) mode++; + }
return mode; } @@ -258,8 +262,11 @@ static int ucsi_register_altmode(struct ucsi_connector *con, goto err; }
- desc->mode = ucsi_altmode_next_mode(con->port_altmode, - desc->svid); + ret = ucsi_altmode_next_mode(con->port_altmode, desc->svid); + if (ret < 0) + return ret; + + desc->mode = ret;
switch (desc->svid) { case USB_TYPEC_DP_SID: @@ -292,8 +299,11 @@ static int ucsi_register_altmode(struct ucsi_connector *con, goto err; }
- desc->mode = ucsi_altmode_next_mode(con->partner_altmode, - desc->svid); + ret = ucsi_altmode_next_mode(con->partner_altmode, desc->svid); + if (ret < 0) + return ret; + + desc->mode = ret;
alt = typec_partner_register_altmode(con->partner, desc); if (IS_ERR(alt)) {