[PATCH 5/8] firmware: arm_ffa: Validate framework notification payload bounds

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

Framework notification callbacks copy an indirect message payload out of
the shared Rx buffer. Validate the reported offset and size before
kmemdup() 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 | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c
index 764cb1226182..0e030f377985 100644
--- a/drivers/firmware/arm_ffa/driver.c
+++ b/drivers/firmware/arm_ffa/driver.c
@@ -1469,6 +1469,7 @@ 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))
@@ -1476,6 +1477,13 @@ static void handle_fwk_notif_callbacks(u32 bitmap)
 
 	scoped_guard(mutex, &drv_info->rx_lock) {
 		msg = drv_info->rx_buffer;
+		if ((msg->offset != min_offset && msg->offset < sizeof(*msg)) ||
+		    msg->offset > drv_info->rxtx_bufsz ||
+		    msg->size > drv_info->rxtx_bufsz - msg->offset) {
+			pr_err("invalid framework notification message\n");
+			goto release_rx;
+		}
+
 		buf = kmemdup((void *)msg + msg->offset, msg->size, GFP_KERNEL);
 		if (!buf)
 			goto release_rx;

-- 
2.43.0