usb: typec: tcpm: Validate SVID index in svdm_consume_modes()

In svdm_consume_modes(), the SVID value is read from pmdata->svids using
pmdata->svid_index as an array index without bounds validation:

    paltmode->svid = pmdata->svids[pmdata->svid_index];

If pmdata->svid_index is driven beyond SVID_DISCOVERY_MAX (16), it results
in an out-of-bounds read of the pmdata->svids array. Because pd_mode_data
is embedded inside struct tcpm_port, indexing past svids reads into
adjacent fields. In particular:
- At index 16, it reads the altmodes count.
- At index 18 and beyond, it reads into altmode_desc[], which contains
  partner-supplied SVDM Discovery Modes VDOs.

By injecting a chosen SVID into altmode_desc[0].vdo and driving svid_index
to 20, the partner can force paltmode->svid to be loaded with an arbitrary,
partner- chosen SVID, which is then registered via
typec_partner_register_altmode().

Fix this by validating that pmdata->svid_index is non-negative and strictly
less than pmdata->nsvids before accessing the pmdata->svids array inside
svdm_consume_modes().

Assisted-by: Antigravity:gemini-3.5-flash
Fixes: 4ab8c18d4d67 ("usb: typec: Register a device for every mode")
Cc: stable <stable@kernel.org>
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Reviewed-by: RD Babiera <rdbabiera@google.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://patch.msgid.link/20260622220803.305750-1-badhri@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index 7ef746a90a17746ff892e94e1049d4f1a8712776..bc531923b1ca966d3534a3f59e1b68e1bc42f5f3 100644 (file)
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -2000,6 +2000,11 @@ static void svdm_consume_modes(struct tcpm_port *port, const u32 *p, int cnt,
                return;
        }
 
+       if (pmdata->svid_index < 0 || pmdata->svid_index >= pmdata->nsvids) {
+               tcpm_log(port, "Invalid SVID index %d", pmdata->svid_index);
+               return;
+       }
+
        for (i = 1; i < cnt; i++) {
                if (pmdata->altmodes >= ALTMODE_DISCOVERY_MAX) {
                        /* Already logged in svdm_consume_svids() */