[PATCH 4.16 079/196] thunderbolt: Prevent crash when ICM firmware is not running

[Greg Kroah-Hartman]

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>

commit ea9d7bb798900096f26c585957d6ad9c532417e6 upstream.

On Lenovo ThinkPad Yoga 370 (and possibly some other Lenovo models as
well) the Thunderbolt host controller sometimes comes up in such way
that the ICM firmware is not running properly. This is most likely an
issue in BIOS/firmware but as side-effect driver crashes the kernel due
to NULL pointer dereference:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000980
  IP: pci_write_config_dword+0x5/0x20
  Call Trace:
   pcie2cio_write+0x3b/0x70 [thunderbolt]
   icm_driver_ready+0x168/0x260 [thunderbolt]
   ? tb_ctl_start+0x50/0x70 [thunderbolt]
   tb_domain_add+0x73/0xf0 [thunderbolt]
   nhi_probe+0x182/0x300 [thunderbolt]
   local_pci_probe+0x42/0xa0
   ? pci_match_device+0xd9/0x100
   pci_device_probe+0x146/0x1b0
   driver_probe_device+0x315/0x480
   ...

Instead of crashing update the driver to bail out gracefully if we
encounter such situation.

Fixes: f67cf491175a ("thunderbolt: Add support for Internal Connection Manager (ICM)")
Reported-by: Jordan Glover <Golden_Miller83@xxxxxxxxxxxxx>
Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Acked-by: Yehezkel Bernat <yehezkel.bernat@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/thunderbolt/icm.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/thunderbolt/icm.c
+++ b/drivers/thunderbolt/icm.c
@@ -923,6 +923,9 @@ static int icm_firmware_reset(struct tb
 	struct icm *icm = tb_priv(tb);
 	u32 val;
 
+	if (!icm->upstream_port)
+		return -ENODEV;
+
 	/* Put ARC to wait for CIO reset event to happen */
 	val = ioread32(nhi->iobase + REG_FW_STS);
 	val |= REG_FW_STS_CIO_RESET_REQ;