[PATCH] PCI: rpaphp: Fix stack overflows when constructing DRC names

[Yudi Yang <2000jedi@gmail.com>]

The drc-name-prefix field of ibm,drc-info is supplied by firmware and
is not limited to fit within MAX_DRC_NAME_LEN. Using sprintf() to append
a suffix can therefore overflow the stack buffers used for DRC names.
Use snprintf() and reject names that would be truncated.

Fixes: 2fcf3ae508c2 ("hotplug/drc-info: Add code to search ibm,drc-info property")
Cc: stable@vger.kernel.org
Signed-off-by: Yudi Yang <2000jedi@gmail.com>
---
 drivers/pci/hotplug/rpaphp_core.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/hotplug/rpaphp_core.c b/drivers/pci/hotplug/rpaphp_core.c
index 2316de0fd198..39109a50fee6 100644
--- a/drivers/pci/hotplug/rpaphp_core.c
+++ b/drivers/pci/hotplug/rpaphp_core.c
@@ -252,8 +252,11 @@ static int rpaphp_check_drc_props_v2(struct device_node *dn, char *drc_name,
 		/* Found it */
 		if (my_index >= drc.drc_index_start && my_index <= drc.last_drc_index) {
 			int index = my_index - drc.drc_index_start;
-			sprintf(cell_drc_name, "%s%d", drc.drc_name_prefix,
-				drc.drc_name_suffix_start + index);
+
+			if (snprintf(cell_drc_name, sizeof(cell_drc_name), "%s%u",
+				     drc.drc_name_prefix,
+				     drc.drc_name_suffix_start + index) >= sizeof(cell_drc_name))
+				return -EINVAL;
 			break;
 		}
 	}
@@ -355,7 +358,9 @@ static int rpaphp_drc_info_add_slot(struct device_node *dn)
 	if (!is_php_type(drc.drc_type))
 		return 0;
 
-	sprintf(drc_name, "%s%d", drc.drc_name_prefix, drc.drc_name_suffix_start);
+	if (snprintf(drc_name, sizeof(drc_name), "%s%u", drc.drc_name_prefix,
+		     drc.drc_name_suffix_start) >= sizeof(drc_name))
+		return -EINVAL;
 
 	slot = alloc_slot_struct(dn, drc.drc_index_start, drc_name, drc.drc_power_domain);
 	if (!slot)
-- 
2.43.0