linux-kernel - [PATCH] usb: typec: tcpm/tcpci_maxim: Fix bounds check in process

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Message-Id: <20250502-b4-new-fix-pd-rx-count-v1-1-e5711ed09b3d@google.com>
Date: Fri, 02 May 2025 16:57:03 -0700
From: Amit Sunil Dhamne via B4 Relay <devnull+amitsd.google.com@...nel.org>
To: Heikki Krogerus <heikki.krogerus@...ux.intel.com>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Badhri Jagan Sridharan <badhri@...gle.com>
Cc: André Draszik <andre.draszik@...aro.org>, 
 Peter Griffin <peter.griffin@...aro.org>, 
 Tudor Ambarus <tudor.ambarus@...aro.org>, RD Babiera <rdbabiera@...gle.com>, 
 linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, 
 stable@...r.kernel.org, Amit Sunil Dhamne <amitsd@...gle.com>, 
 Kyle Tso <kyletso@...gle.com>
Subject: [PATCH] usb: typec: tcpm/tcpci_maxim: Fix bounds check in
 process_rx()

From: Amit Sunil Dhamne <amitsd@...gle.com>

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@...gle.com>
Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>
Reviewed-by: Kyle Tso <kyletso@...gle.com>
---
 drivers/usb/typec/tcpm/tcpci_maxim_core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/typec/tcpm/tcpci_maxim_core.c b/drivers/usb/typec/tcpm/tcpci_maxim_core.c
index fd1b80593367641a6f997da2fb97a2b7238f6982..648311f5e3cf135f23b5cc0668001d2f177b9edd 100644
--- a/drivers/usb/typec/tcpm/tcpci_maxim_core.c
+++ b/drivers/usb/typec/tcpm/tcpci_maxim_core.c
@@ -166,7 +166,8 @@ 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;
 	}

---
base-commit: ebd297a2affadb6f6f4d2e5d975c1eda18ac762d
change-id: 20250421-b4-new-fix-pd-rx-count-79297ba619b7

Best regards,
-- 
Amit Sunil Dhamne <amitsd@...gle.com>