7.2-stable review patch. If anyone has any objections, please let me know.
------------------
From: Anthony Krowiak <akrowiak@linux.ibm.com>
commit bf09b9d7cd7890bc3a3b7eb63d5ece15f88bfde7 upstream.
The DECLARE_BITMAP(apm_filtered, AP_DEVICES) macro allocates the bitmap
on the stack without zero-initializing it.
In vfio_ap_mdev_hot_plug_cfg(), the vfio_ap_mdev_filter_matrix() function
is only called to initialize and populate apm_filtered if either
filter_adapters or filter_domains is true. If the hot plug configuration
change only adds control domains (meaning filter_cdoms is true, but
filter_adapters and filter_domains are both false),
vfio_ap_mdev_filter_matrix() is bypassed.
Consequently, apm_filtered is passed to reset_queues_for_apids() with
uninitialized stack garbage. This can cause reset_queues_for_apids() to
interpret arbitrary stack garbage bits as valid APIDs to reset, potentially
performing unintended guest hardware queue resets.
Fix this by zero-initializing the apm_filtered bitmap at the beginning of
vfio_ap_mdev_hot_plug_cfg() using bitmap_zero().
Fixes: eeb386aeb5b7c ("s390/vfio-ap: handle config changed and scan complete notification")
Cc: <redacted>
Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/s390/crypto/vfio_ap_ops.c | 9 +++++++++
1 file changed, 9 insertions(+)
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -2877,6 +2877,15 @@ static void vfio_ap_mdev_hot_plug_cfg(st
DECLARE_BITMAP(apm_filtered, AP_DEVICES);
bool filter_domains, filter_adapters, filter_cdoms, do_hotplug = false;
+ /*
+ * Zero out the apm_filtered bitmap in case there are no adapters or
+ * domains to be added, but only control domains. In that case,
+ * vfio_ap_mdev_filter_matrix() - which initializes apm_filtered - will
+ * not get called and the reset_queues_for_apids will crash because it
+ * will access an uninitialized bitmap.
+ */
+ bitmap_zero(apm_filtered, AP_DEVICES);
+
filter_adapters = bitmap_intersects(matrix_mdev->matrix.apm,
matrix_mdev->apm_add, AP_DEVICES);
filter_domains = bitmap_intersects(matrix_mdev->matrix.aqm,