[PATCH v6] net: wwan: t7xx: validate port_count against message length in t7xx_port_enum_msg_handler

[Pavitra Jha <jhapavitra98@gmail.com>]

t7xx_port_enum_msg_handler() uses the modem-supplied port_count field as
a loop bound over port_msg->data[] without checking that the message buffer
contains sufficient data. A modem sending port_count=65535 in a 12-byte
buffer triggers a slab-out-of-bounds read of up to 262140 bytes.

Add a sizeof(*port_msg) check before accessing the port message header
fields to guard against undersized messages.

Add a struct_size() check after extracting port_count and before the loop.

In t7xx_parse_host_rt_data(), guard the rt_feature header read with a
remaining-buffer check before accessing data_len, validate feat_data_len
against the actual remaining buffer to prevent OOB reads and signed
integer overflow on offset.

Pass msg_len from both call sites: skb->len at the DPMAIF path after
skb_pull(), and the validated feat_data_len at the handshake path.

Fixes: da45d2566a1d ("net: wwan: t7xx: Add control port")
Cc: stable@vger.kernel.org
Signed-off-by: Pavitra Jha <jhapavitra98@gmail.com>
---
 drivers/net/wwan/t7xx/t7xx_modem_ops.c     | 20 +++++++++++++++++---
 drivers/net/wwan/t7xx/t7xx_port_ctrl_msg.c | 18 ++++++++++++++++--
 drivers/net/wwan/t7xx/t7xx_port_proxy.h    |  2 +-
 3 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/drivers/net/wwan/t7xx/t7xx_modem_ops.c b/drivers/net/wwan/t7xx/t7xx_modem_ops.c
index 7968e208d..adb29d30c 100644
--- a/drivers/net/wwan/t7xx/t7xx_modem_ops.c
+++ b/drivers/net/wwan/t7xx/t7xx_modem_ops.c
@@ -457,8 +457,20 @@ static int t7xx_parse_host_rt_data(struct t7xx_fsm_ctl *ctl, struct t7xx_sys_inf
 
 	offset = sizeof(struct feature_query);
 	for (i = 0; i < FEATURE_COUNT && offset < data_length; i++) {
+		size_t remaining = data_length - offset;
+		size_t feat_data_len, feat_total;
+
+		if (remaining < sizeof(*rt_feature))
+			break;
+
 		rt_feature = data + offset;
-		offset += sizeof(*rt_feature) + le32_to_cpu(rt_feature->data_len);
+		feat_data_len = le32_to_cpu(rt_feature->data_len);
+
+		if (feat_data_len > remaining - sizeof(*rt_feature))
+			break;
+
+		feat_total = sizeof(*rt_feature) + feat_data_len;
+		offset += feat_total;
 
 		ft_spt_cfg = FIELD_GET(FEATURE_MSK, core->feature_set[i]);
 		if (ft_spt_cfg != MTK_FEATURE_MUST_BE_SUPPORTED)
@@ -468,8 +480,10 @@ static int t7xx_parse_host_rt_data(struct t7xx_fsm_ctl *ctl, struct t7xx_sys_inf
 		if (ft_spt_st != MTK_FEATURE_MUST_BE_SUPPORTED)
 			return -EINVAL;
 
-		if (i == RT_ID_MD_PORT_ENUM || i == RT_ID_AP_PORT_ENUM)
-			t7xx_port_enum_msg_handler(ctl->md, rt_feature->data);
+		if (i == RT_ID_MD_PORT_ENUM || i == RT_ID_AP_PORT_ENUM) {
+			t7xx_port_enum_msg_handler(ctl->md, rt_feature->data,
+						   feat_data_len);
+		}
 	}
 
 	return 0;
diff --git a/drivers/net/wwan/t7xx/t7xx_port_ctrl_msg.c b/drivers/net/wwan/t7xx/t7xx_port_ctrl_msg.c
index ae632ef96..f869e4ed9 100644
--- a/drivers/net/wwan/t7xx/t7xx_port_ctrl_msg.c
+++ b/drivers/net/wwan/t7xx/t7xx_port_ctrl_msg.c
@@ -117,6 +117,7 @@ static int fsm_ee_message_handler(struct t7xx_port *port, struct t7xx_fsm_ctl *c
  * t7xx_port_enum_msg_handler() - Parse the port enumeration message to create/remove nodes.
  * @md: Modem context.
  * @msg: Message.
+ * @msg_len:	Length of @msg in bytes.
  *
  * Used to control create/remove device node.
  *
@@ -124,12 +125,18 @@ static int fsm_ee_message_handler(struct t7xx_port *port, struct t7xx_fsm_ctl *c
  * * 0		- Success.
  * * -EFAULT	- Message check failure.
  */
-int t7xx_port_enum_msg_handler(struct t7xx_modem *md, void *msg)
+int t7xx_port_enum_msg_handler(struct t7xx_modem *md, void *msg, size_t msg_len)
 {
 	struct device *dev = &md->t7xx_dev->pdev->dev;
 	unsigned int version, port_count, i;
 	struct port_msg *port_msg = msg;
 
+	if (msg_len < sizeof(*port_msg)) {
+		dev_err(dev, "Port enum msg too short for header: need %zu, have %zu\n",
+			sizeof(*port_msg), msg_len);
+		return -EINVAL;
+	}
+
 	version = FIELD_GET(PORT_MSG_VERSION, le32_to_cpu(port_msg->info));
 	if (version != PORT_ENUM_VER ||
 	    le32_to_cpu(port_msg->head_pattern) != PORT_ENUM_HEAD_PATTERN ||
@@ -141,6 +148,13 @@ int t7xx_port_enum_msg_handler(struct t7xx_modem *md, void *msg)
 	}
 
 	port_count = FIELD_GET(PORT_MSG_PRT_CNT, le32_to_cpu(port_msg->info));
+
+	if (msg_len < struct_size(port_msg, data, port_count)) {
+		dev_err(dev, "Port enum msg too short: need %zu, have %zu\n",
+			struct_size(port_msg, data, port_count), msg_len);
+		return -EINVAL;
+	}
+
 	for (i = 0; i < port_count; i++) {
 		u32 port_info = le32_to_cpu(port_msg->data[i]);
 		unsigned int ch_id;
@@ -191,7 +205,7 @@ static int control_msg_handler(struct t7xx_port *port, struct sk_buff *skb)
 
 	case CTL_ID_PORT_ENUM:
 		skb_pull(skb, sizeof(*ctrl_msg_h));
-		ret = t7xx_port_enum_msg_handler(ctl->md, (struct port_msg *)skb->data);
+		ret = t7xx_port_enum_msg_handler(ctl->md, (struct port_msg *)skb->data, skb->len);
 		if (!ret)
 			ret = port_ctl_send_msg_to_md(port, CTL_ID_PORT_ENUM, 0);
 		else
diff --git a/drivers/net/wwan/t7xx/t7xx_port_proxy.h b/drivers/net/wwan/t7xx/t7xx_port_proxy.h
index f0918b36e..7c3190bf0 100644
--- a/drivers/net/wwan/t7xx/t7xx_port_proxy.h
+++ b/drivers/net/wwan/t7xx/t7xx_port_proxy.h
@@ -103,7 +103,7 @@ void t7xx_port_proxy_reset(struct port_proxy *port_prox);
 void t7xx_port_proxy_uninit(struct port_proxy *port_prox);
 int t7xx_port_proxy_init(struct t7xx_modem *md);
 void t7xx_port_proxy_md_status_notify(struct port_proxy *port_prox, unsigned int state);
-int t7xx_port_enum_msg_handler(struct t7xx_modem *md, void *msg);
+int t7xx_port_enum_msg_handler(struct t7xx_modem *md, void *msg, size_t msg_len);
 int t7xx_port_proxy_chl_enable_disable(struct port_proxy *port_prox, unsigned int ch_id,
 				       bool en_flag);
 void t7xx_port_proxy_set_cfg(struct t7xx_modem *md, enum port_cfg_id cfg_id);
-- 
2.53.0