From 2c10636a0b9c689450e85f9945583920f50337c9 Mon Sep 17 00:00:00 2001
From: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Date: Thu, 15 Feb 2018 21:27:41 -0600
Subject: [PATCH] powerpc/pseries: Check for zero filled ibm,dynamic-memory
 property

References: FATE#324825, bsc#1077428, bsc#1080789
Patch-mainline: v4.16-rc2
Git-commit: 2c10636a0b9c689450e85f9945583920f50337c9

Some versions of QEMU will produce an ibm,dynamic-reconfiguration-memory
node with a ibm,dynamic-memory property that is zero-filled. This
causes the drmem code to oops trying to parse this property.

The fix for this is to validate that the property does contain LMB
entries before trying to parse it and bail if the count is zero.

  Oops: Kernel access of bad area, sig: 11 [#1]
  DAR: 0000000000000010
  NIP read_drconf_v1_cell+0x54/0x9c
  LR  read_drconf_v1_cell+0x48/0x9c
  Call Trace:
    __param_initcall_debug+0x0/0x28 (unreliable)
    drmem_init+0x144/0x2f8
    do_one_initcall+0x64/0x1d0
    kernel_init_freeable+0x298/0x38c
    kernel_init+0x24/0x160
    ret_from_kernel_thread+0x5c/0xb4

The ibm,dynamic-reconfiguration-memory device tree property generated
that causes this:

  ibm,dynamic-reconfiguration-memory {
          ibm,lmb-size = <0x0 0x10000000>;
          ibm,memory-flags-mask = <0xff>;
          ibm,dynamic-memory = <0x0 0x0 0x0 0x0 0x0 0x0>;
          linux,phandle = <0x7e57eed8>;
          ibm,associativity-lookup-arrays = <0x1 0x4 0x0 0x0 0x0 0x0>;
          ibm,memory-preservation-time = <0x0>;
  };

Signed-off-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Reviewed-by: Cyril Bur <cyrilbur@gmail.com>
Tested-by: Daniel Black <daniel@linux.vnet.ibm.com>
[mpe: Trim oops report]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
 arch/powerpc/mm/drmem.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/powerpc/mm/drmem.c b/arch/powerpc/mm/drmem.c
index 1604110c4238..916844f99c64 100644
--- a/arch/powerpc/mm/drmem.c
+++ b/arch/powerpc/mm/drmem.c
@@ -216,6 +216,8 @@ static void __init __walk_drmem_v1_lmbs(const __be32 *prop, const __be32 *usm,
 	u32 i, n_lmbs;
 
 	n_lmbs = of_read_number(prop++, 1);
+	if (n_lmbs == 0)
+		return;
 
 	for (i = 0; i < n_lmbs; i++) {
 		read_drconf_v1_cell(&lmb, &prop);
@@ -245,6 +247,8 @@ static void __init __walk_drmem_v2_lmbs(const __be32 *prop, const __be32 *usm,
 	u32 i, j, lmb_sets;
 
 	lmb_sets = of_read_number(prop++, 1);
+	if (lmb_sets == 0)
+		return;
 
 	for (i = 0; i < lmb_sets; i++) {
 		read_drconf_v2_cell(&dr_cell, &prop);
@@ -354,6 +358,8 @@ static void __init init_drmem_v1_lmbs(const __be32 *prop)
 	struct drmem_lmb *lmb;
 
 	drmem_info->n_lmbs = of_read_number(prop++, 1);
+	if (drmem_info->n_lmbs == 0)
+		return;
 
 	drmem_info->lmbs = kcalloc(drmem_info->n_lmbs, sizeof(*lmb),
 				   GFP_KERNEL);
@@ -373,6 +379,8 @@ static void __init init_drmem_v2_lmbs(const __be32 *prop)
 	int lmb_index;
 
 	lmb_sets = of_read_number(prop++, 1);
+	if (lmb_sets == 0)
+		return;
 
 	/* first pass, calculate the number of LMBs */
 	p = prop;
-- 
2.13.6