[RFC v3 1/4] powerpc/hotplug/drcinfo: Fix bugs parsing ibm,drc-info structs

[Michael Bringmann]

[Replace/withdraw previous patch submission to ensure that testing
of related patches on similar hardware progresses together.]

This patch fixes a memory parsing bug when using of_prop_next_u32
calls at the start of a structure.  Depending upon the value of
"cur" memory pointer argument to of_prop_next_u32, it will or it
won't advance the value of the returned memory pointer by the
size of one u32.  This patch corrects the code to deal with that
indexing feature when parsing the ibm,drc-info structs for CPUs.
Also, need to advance the pointer at the end of_read_drc_info_cell
for same reason.

Signed-off-by: Michael Bringmann <mwb at linux.vnet.ibm.com>
Fixes: 3f38000eda48 ("powerpc/firmware: Add definitions for new drc-info firmware feature" -- end of patch series applied to powerpc next)
---
Changes in V3:
  -- Rebased patch to 4.17-rc5 kernel
---
 arch/powerpc/platforms/pseries/of_helpers.c     |    5 ++---
 arch/powerpc/platforms/pseries/pseries_energy.c |    2 ++
 drivers/pci/hotplug/rpaphp_core.c               |    1 +
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/of_helpers.c b/arch/powerpc/platforms/pseries/of_helpers.c
index 6df192f..20598b2 100644
--- a/arch/powerpc/platforms/pseries/of_helpers.c
+++ b/arch/powerpc/platforms/pseries/of_helpers.c
@@ -65,9 +65,7 @@ int of_read_drc_info_cell(struct property **prop, const __be32 **curval,
 
 	/* Get drc-index-start:encode-int */
 	p2 = (const __be32 *)p;
-	p2 = of_prop_next_u32(*prop, p2, &data->drc_index_start);
-	if (!p2)
-		return -EINVAL;
+	data->drc_index_start = of_read_number(p2, 1);
 
 	/* Get drc-name-suffix-start:encode-int */
 	p2 = of_prop_next_u32(*prop, p2, &data->drc_name_suffix_start);
@@ -88,6 +86,7 @@ int of_read_drc_info_cell(struct property **prop, const __be32 **curval,
 	p2 = of_prop_next_u32(*prop, p2, &data->drc_power_domain);
 	if (!p2)
 		return -EINVAL;
+	p2++;
 
 	/* Should now know end of current entry */
 	(*curval) = (void *)p2;
diff --git a/arch/powerpc/platforms/pseries/pseries_energy.c b/arch/powerpc/platforms/pseries/pseries_energy.c
index 6ed2212..c7d84aa 100644
--- a/arch/powerpc/platforms/pseries/pseries_energy.c
+++ b/arch/powerpc/platforms/pseries/pseries_energy.c
@@ -64,6 +64,7 @@ static u32 cpu_to_drc_index(int cpu)
 		value = of_prop_next_u32(info, NULL, &num_set_entries);
 		if (!value)
 			goto err_of_node_put;
+		value++;
 
 		for (j = 0; j < num_set_entries; j++) {
 
@@ -126,6 +127,7 @@ static int drc_index_to_cpu(u32 drc_index)
 		value = of_prop_next_u32(info, NULL, &num_set_entries);
 		if (!value)
 			goto err_of_node_put;
+		value++;
 
 		for (j = 0; j < num_set_entries; j++) {
 
diff --git a/drivers/pci/hotplug/rpaphp_core.c b/drivers/pci/hotplug/rpaphp_core.c
index fb5e084..dccdf62 100644
--- a/drivers/pci/hotplug/rpaphp_core.c
+++ b/drivers/pci/hotplug/rpaphp_core.c
@@ -239,6 +239,7 @@ static int rpaphp_check_drc_props_v2(struct device_node *dn, char *drc_name,
 	value = of_prop_next_u32(info, NULL, &entries);
 	if (!value)
 		return -EINVAL;
+	value++;
 
 	for (j = 0; j < entries; j++) {
 		of_read_drc_info_cell(&info, &value, &drc);