rpmsg: validate incoming message length before propagating
When an inbound message arrives, validate its reported length before
propagating it, otherwise buggy (or malicious) remote processors might
trick us into accessing memory which we really shouldn't.
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Mark Grosen <mgrosen@ti.com>
Cc: Suman Anna <s-anna@ti.com>
Cc: Fernando Guzman Lugo <fernando.lugo@ti.com>
Cc: Rob Clark <rob@ti.com>
Cc: Ludovic BARRE <ludovic.barre@stericsson.com>
Cc: Loic PALLARDY <loic.pallardy@stericsson.com>
Cc: Omar Ramirez Luna <omar.luna@linaro.org>
diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
index 4db9cf8..1e8b8b6 100644
--- a/drivers/rpmsg/virtio_rpmsg_bus.c
+++ b/drivers/rpmsg/virtio_rpmsg_bus.c
@@ -778,6 +778,16 @@
print_hex_dump(KERN_DEBUG, "rpmsg_virtio RX: ", DUMP_PREFIX_NONE, 16, 1,
msg, sizeof(*msg) + msg->len, true);
+ /*
+ * We currently use fixed-sized buffers, so trivially sanitize
+ * the reported payload length.
+ */
+ if (len > RPMSG_BUF_SIZE ||
+ msg->len > (len - sizeof(struct rpmsg_hdr))) {
+ dev_warn(dev, "inbound msg too big: (%d, %d)\n", len, msg->len);
+ return;
+ }
+
/* use the dst addr to fetch the callback of the appropriate user */
mutex_lock(&vrp->endpoints_lock);
ept = idr_find(&vrp->endpoints, msg->dst);