[PATCH 5.2 394/413] powerpc/pseries: Fix oops in hotplug memory notifier

From: Greg Kroah-Hartman
Date: Wed Jul 24 2019 - 16:24:06 EST

From: Nathan Lynch <nathanl@xxxxxxxxxxxxx>

commit 0aa82c482ab2ece530a6f44897b63b274bb43c8e upstream.

During post-migration device tree updates, we can oops in
pseries_update_drconf_memory() if the source device tree has an
ibm,dynamic-memory-v2 property and the destination has a
ibm,dynamic_memory (v1) property. The notifier processes an "update"
for the ibm,dynamic-memory property but it's really an add in this
scenario. So make sure the old property object is there before
dereferencing it.

Fixes: 2b31e3aec1db ("powerpc/drmem: Add support for ibm, dynamic-memory-v2 property")
Cc: stable@xxxxxxxxxxxxxxx # v4.16+
Signed-off-by: Nathan Lynch <nathanl@xxxxxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/powerpc/platforms/pseries/hotplug-memory.c | 3 +++
1 file changed, 3 insertions(+)

--- a/arch/powerpc/platforms/pseries/hotplug-memory.c
+++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
@@ -976,6 +976,9 @@ static int pseries_update_drconf_memory(
if (!memblock_size)
return -EINVAL;

+ if (!pr->old_prop)
+ return 0;
p = (__be32 *) pr->old_prop->value;
if (!p)
return -EINVAL;