usb: typec: tcpm/tcpci_maxim: Fix bounds check in process_rx()

commit 0736299d090f5c6a1032678705c4bc0a9511a3db upstream.

Register read of TCPC_RX_BYTE_CNT returns the total size consisting of:

  PD message (pending read) size + 1 Byte for Frame Type (SOP*)

This is validated against the max PD message (`struct pd_message`) size
without accounting for the extra byte for the frame type. Note that the
struct pd_message does not contain a field for the frame_type. This
results in false negatives when the "PD message (pending read)" is equal
to the max PD message size.

Fixes: 6f413b559f86 ("usb: typec: tcpci_maxim: Chip level TCPC driver")
Signed-off-by: Amit Sunil Dhamne <amitsd@google.com>
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Reviewed-by: Kyle Tso <kyletso@google.com>
Cc: stable <stable@kernel.org>
Link: https://lore.kernel.org/stable/20250502-b4-new-fix-pd-rx-count-v1-1-e5711ed09b3d%40google.com
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20250502-b4-new-fix-pd-rx-count-v1-1-e5711ed09b3d@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/typec/tcpm/tcpci_maxim.c b/drivers/usb/typec/tcpm/tcpci_maxim.c
index 4b6705f3d7b78000a1855ef7441de8a9676a3492..a602f4f512821c8b271aa98b6f08fc9b3930da99 100644 (file)
--- a/drivers/usb/typec/tcpm/tcpci_maxim.c
+++ b/drivers/usb/typec/tcpm/tcpci_maxim.c
@@ -171,7 +171,8 @@ static void process_rx(struct max_tcpci_chip *chip, u16 status)
                return;
        }
 
-       if (count > sizeof(struct pd_message) || count + 1 > TCPC_RECEIVE_BUFFER_LEN) {
+       if (count > sizeof(struct pd_message) + 1 ||
+           count + 1 > TCPC_RECEIVE_BUFFER_LEN) {
                dev_err(chip->dev, "Invalid TCPC_RX_BYTE_CNT %d\n", count);
                return;
        }