firmware: imx: warn on unexpected RX

The imx_scu_call_rpc function returns the result inside the
same "msg" struct containing the transmitted message. This is
implemented by holding a pointer to msg (which is usually on the stack)
in sc_imx_rpc and writing to it from imx_scu_rx_callback.

This means that if the have_resp parameter is incorrect or SCU sends an
unexpected response for any reason the most likely result is kernel stack
corruption.

Fix this by only setting sc_imx_rpc.msg for the duration of the
imx_scu_call_rpc call and warning in imx_scu_rx_callback if unset.

Print the unexpected response data to help debugging.

Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Acked-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

diff --git a/drivers/firmware/imx/imx-scu.c b/drivers/firmware/imx/imx-scu.c
index 04a24a863d6ef7e9884808592ae8363328cdf404..869be7a5172cf8aebd053a1974895366bd937f4f 100644 (file)
--- a/drivers/firmware/imx/imx-scu.c
+++ b/drivers/firmware/imx/imx-scu.c
@@ -107,6 +107,12 @@ static void imx_scu_rx_callback(struct mbox_client *c, void *msg)
        struct imx_sc_rpc_msg *hdr;
        u32 *data = msg;
 
+       if (!sc_ipc->msg) {
+               dev_warn(sc_ipc->dev, "unexpected rx idx %d 0x%08x, ignore!\n",
+                               sc_chan->idx, *data);
+               return;
+       }
+
        if (sc_chan->idx == 0) {
                hdr = msg;
                sc_ipc->rx_size = hdr->size;
@@ -165,7 +171,8 @@ int imx_scu_call_rpc(struct imx_sc_ipc *sc_ipc, void *msg, bool have_resp)
        mutex_lock(&sc_ipc->lock);
        reinit_completion(&sc_ipc->done);
 
-       sc_ipc->msg = msg;
+       if (have_resp)
+               sc_ipc->msg = msg;
        sc_ipc->count = 0;
        ret = imx_scu_ipc_write(sc_ipc, msg);
        if (ret < 0) {
@@ -187,6 +194,7 @@ int imx_scu_call_rpc(struct imx_sc_ipc *sc_ipc, void *msg, bool have_resp)
        }
 
 out:
+       sc_ipc->msg = NULL;
        mutex_unlock(&sc_ipc->lock);
 
        dev_dbg(sc_ipc->dev, "RPC SVC done\n");