[PATCH v2 08/11] firmware: arm_ffa: Validate framework notification message layout

[Sudeep Holla <sudeep.holla@kernel.org>]

Framework notifications carry an indirect message in the shared RX
buffer. Validate the reported offset and size before using them, reject
zero-length payloads, and ensure that any non-header payload starts at
the UUID field rather than in the middle of the message header.

Use the validated offset and size values for both kmemdup() and the UUID
parsing path so malformed firmware data cannot drive an out-of-bounds
read or an oversized allocation.

Fixes: 285a5ea0f542 ("firmware: arm_ffa: Add support for handling framework notifications")
Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>
---
 drivers/firmware/arm_ffa/driver.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c
index 18bcbd161805..4944aa6b815f 100644
--- a/drivers/firmware/arm_ffa/driver.c
+++ b/drivers/firmware/arm_ffa/driver.c
@@ -1489,21 +1489,35 @@ static void handle_fwk_notif_callbacks(u32 bitmap)
 	int notify_id = 0, target;
 	struct ffa_indirect_msg_hdr *msg;
 	struct notifier_cb_info *cb_info = NULL;
+	size_t min_offset = offsetof(struct ffa_indirect_msg_hdr, uuid);
 
 	/* Only one framework notification defined and supported for now */
 	if (!(bitmap & FRAMEWORK_NOTIFY_RX_BUFFER_FULL))
 		return;
 
 	scoped_guard(mutex, &drv_info->rx_lock) {
+		u32 offset, size;
+
 		msg = drv_info->rx_buffer;
-		buf = kmemdup((void *)msg + msg->offset, msg->size, GFP_KERNEL);
+		offset = msg->offset;
+		size = msg->size;
+
+		if (!size || (offset != min_offset && offset < sizeof(*msg)) ||
+		    offset > drv_info->rxtx_bufsz ||
+		    size > drv_info->rxtx_bufsz - offset) {
+			pr_err("invalid framework notification message\n");
+			ffa_rx_release();
+			return;
+		}
+
+		buf = kmemdup((void *)msg + offset, size, GFP_KERNEL);
 		if (!buf) {
 			ffa_rx_release();
 			return;
 		}
 
 		target = SENDER_ID(msg->send_recv_id);
-		if (msg->offset >= sizeof(*msg))
+		if (offset >= sizeof(*msg))
 			uuid_copy(&uuid, &msg->uuid);
 		else
 			uuid_copy(&uuid, &uuid_null);

-- 
2.43.0