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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Nathan Lynch <nathanl@linux.ibm.com>,
        Michael Ellerman <mpe@ellerman.id.au>
Subject: [PATCH 5.1 355/371] powerpc/pseries: Fix oops in hotplug memory notifier
Date:   Wed, 24 Jul 2019 21:21:47 +0200
Message-Id: <20190724191750.642398704@linuxfoundation.org>
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From: Nathan Lynch <nathanl@linux.ibm.com>

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@vger.kernel.org # v4.16+
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 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
@@ -980,6 +980,9 @@ 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;