From 3389c149c68c3fea61910ad5d34f7bf3bff44e32 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Wed, 13 May 2026 17:52:53 +0200 Subject: [PATCH] usb: typec: tcpm: bound altmode_desc[] per iteration in svdm_consume_modes() svdm_consume_modes() checks pmdata->altmodes against the array size once before the loop over the count, but forgot to check the bound at every point in the loop. In the well-behaved SVDM discovery flow this is harmless because each of at most SVID_DISCOVERY_MAX SVIDs contributes at most MODE_DISCOVERY_MAX modes, exactly filling altmode_desc[ALTMODE_DISCOVERY_MAX]. But the CMDT_RSP_ACK handler in tcpm_pd_svdm() does not correlate an incoming ACK with any request the port actually sent. Once port->partner is set, an unsolicited Discover Modes ACK is consumed unconditionally. A broken or malicious port partner can therefore drive altmodes to ALTMODE_DISCOVERY_MAX - 1 via the normal flow, and then send one extra Discover Modes ACK with seven VDOs. Because the pre-loop check passes, the loop could then writes up to five entries past altmode_desc[]. For mode_data_prime the next field in struct tcpm_port is the partner_altmode[] pointer array, which then receives partner-chosen SVID/VDO bytes. Move the bound check inside the loop so the array can never be indexed past ALTMODE_DISCOVERY_MAX regardless of how many VDOs the partner supplies or how the function was reached. Assisted-by: gkh_clanker_t1000 Cc: Badhri Jagan Sridharan Cc: Heikki Krogerus Cc: stable Link: https://patch.msgid.link/2026051351-reshuffle-skillful-90af@gregkh Signed-off-by: Greg Kroah-Hartman --- drivers/usb/typec/tcpm/tcpm.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-) diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c index 44dab6c32c33..ed5f745a8231 100644 --- a/drivers/usb/typec/tcpm/tcpm.c +++ b/drivers/usb/typec/tcpm/tcpm.c @@ -1992,23 +1992,19 @@ static void svdm_consume_modes(struct tcpm_port *port, const u32 *p, int cnt, switch (rx_sop_type) { case TCPC_TX_SOP_PRIME: pmdata = &port->mode_data_prime; - if (pmdata->altmodes >= ARRAY_SIZE(port->plug_prime_altmode)) { - /* Already logged in svdm_consume_svids() */ - return; - } break; case TCPC_TX_SOP: pmdata = &port->mode_data; - if (pmdata->altmodes >= ARRAY_SIZE(port->partner_altmode)) { - /* Already logged in svdm_consume_svids() */ - return; - } break; default: return; } for (i = 1; i < cnt; i++) { + if (pmdata->altmodes >= ALTMODE_DISCOVERY_MAX) { + /* Already logged in svdm_consume_svids() */ + return; + } paltmode = &pmdata->altmode_desc[pmdata->altmodes]; memset(paltmode, 0, sizeof(*paltmode));