intel_th: Fix device removal logic

commit 8801922cd94c918e4dc3a108ecaa500c4d40583f upstream.

Commit a753bfcfdb1f ("intel_th: Make the switch allocate its subdevices")
brings in new subdevice addition/removal logic that's broken for "host
mode": the SWITCH device has no children to begin with, which is not
handled in the code. This results in a null dereference bug later down
the path.

This patch fixes the subdevice removal code to handle host mode correctly.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Fixes: a753bfcfdb1f ("intel_th: Make the switch allocate its subdevices")
CC: stable@vger.kernel.org # v4.14+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hwtracing/intel_th/core.c b/drivers/hwtracing/intel_th/core.c
index c1793313bb0873fea10e263062f6e580d34c7670..757801d2760439ac116acc52a0995af618331125 100644 (file)
--- a/drivers/hwtracing/intel_th/core.c
+++ b/drivers/hwtracing/intel_th/core.c
@@ -147,7 +147,8 @@ static int intel_th_remove(struct device *dev)
                        th->thdev[i] = NULL;
                }
 
-               th->num_thdevs = lowest;
+               if (lowest >= 0)
+                       th->num_thdevs = lowest;
        }
 
        if (thdrv->attr_group)