releases/4.19.51/platform-chrome-cros_ec_proto-check-for-null-transfe.patch

   1 From 46cb12e7892f73be3038993da8cd9419c8284a6a Mon Sep 17 00:00:00 2001
   2 From: Enrico Granata <egranata@chromium.org>
   3 Date: Wed, 3 Apr 2019 15:40:36 -0700
   4 Subject: platform/chrome: cros_ec_proto: check for NULL transfer function
   5
   6 [ Upstream commit 94d4e7af14a1170e34cf082d92e4c02de9e9fb88 ]
   7
   8 As new transfer mechanisms are added to the EC codebase, they may
   9 not support v2 of the EC protocol.
  10
  11 If the v3 initial handshake transfer fails, the kernel will try
  12 and call cmd_xfer as a fallback. If v2 is not supported, cmd_xfer
  13 will be NULL, and the code will end up causing a kernel panic.
  14
  15 Add a check for NULL before calling the transfer function, along
  16 with a helpful comment explaining how one might end up in this
  17 situation.
  18
  19 Signed-off-by: Enrico Granata <egranata@chromium.org>
  20 Reviewed-by: Jett Rink <jettrink@chromium.org>
  21 Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
  22 Signed-off-by: Sasha Levin <sashal@kernel.org>
  23 ---
  24  drivers/platform/chrome/cros_ec_proto.c | 11 +++++++++++
  25  1 file changed, 11 insertions(+)
  26
  27 diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
  28 index e5d5b1adb5a9..ac784ac66ac3 100644
  29 --- a/drivers/platform/chrome/cros_ec_proto.c
  30 +++ b/drivers/platform/chrome/cros_ec_proto.c
  31 @@ -67,6 +67,17 @@ static int send_command(struct cros_ec_device *ec_dev,
  32         else
  33                 xfer_fxn = ec_dev->cmd_xfer;
  34
  35 +       if (!xfer_fxn) {
  36 +               /*
  37 +                * This error can happen if a communication error happened and
  38 +                * the EC is trying to use protocol v2, on an underlying
  39 +                * communication mechanism that does not support v2.
  40 +                */
  41 +               dev_err_once(ec_dev->dev,
  42 +                            "missing EC transfer API, cannot send command\n");
  43 +               return -EIO;
  44 +       }
  45 +
  46         ret = (*xfer_fxn)(ec_dev, msg);
  47         if (msg->result == EC_RES_IN_PROGRESS) {
  48                 int i;
  49 --
  50 2.20.1
  51