[PATCH 4.9 44/61] powerpc/pseries: Restore default security feature flags on setup

Greg Kroah-Hartman
2018-06-05T17:12:54Z

From: Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>

commit 6232774f1599028a15418179d17f7df47ede770a upstream.

After migration the security feature flags might have changed (e.g.,
destination system with unpatched firmware), but some flags are not
set/clear again in init_cpu_char_feature_flags() because it assumes
the security flags to be the defaults.

Additionally, if the H_GET_CPU_CHARACTERISTICS hypercall fails then
init_cpu_char_feature_flags() does not run again, which potentially
might leave the system in an insecure or sub-optimal configuration.

So, just restore the security feature flags to the defaults assumed
by init_cpu_char_feature_flags() so it can set/clear them correctly,
and to ensure safe settings are in place in case the hypercall fail.

Fixes: f636c14790ea ("powerpc/pseries: Set or clear security feature flags")
Depends-on: 19887d6a28e2 ("powerpc: Move default security feature flags")
Signed-off-by: Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/powerpc/platforms/pseries/setup.c | 11 +++++++++++
1 file changed, 11 insertions(+)

--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -453,6 +453,10 @@ static void __init find_and_init_phbs(vo

static void init_cpu_char_feature_flags(struct h_cpu_char_result *result)
{
+ /*
+ * The features below are disabled by default, so we instead look to see
+ * if firmware has *enabled* them, and set them if so.
+ */
if (result->character & H_CPU_CHAR_SPEC_BAR_ORI31)
security_ftr_set(SEC_FTR_SPEC_BAR_ORI31);

@@ -492,6 +496,13 @@ void pseries_setup_rfi_flush(void)
bool enable;
long rc;

+ /*
+ * Set features to the defaults assumed by init_cpu_char_feature_flags()
+ * so it can set/clear again any features that might have changed after
+ * migration, and in case the hypercall fails and it is not even called.
+ */
+ powerpc_security_features = SEC_FTR_DEFAULT;
+
rc = plpar_get_cpu_characteristics(&result);
if (rc == H_SUCCESS)
init_cpu_char_feature_flags(&result);