[PATCH 5.1 044/121] fpga: stratix10-soc: fix use-after-free on s10_init()

From: Greg Kroah-Hartman
Date: Mon Jun 24 2019 - 06:10:10 EST

[ Upstream commit f5dd87326fefe42a4b1a4b1a1a695060c33a88d6 ]

The refcount of fw_np has already been decreased by of_find_matching_node()
so it shouldn't be used anymore.
This patch adds an of_node_get() before of_find_matching_node() to avoid
the use-after-free problem.

Fixes: e7eef1d7633a ("fpga: add intel stratix10 soc fpga manager driver")
Signed-off-by: Wen Yang <wen.yang99@xxxxxxxxxx>
Cc: Alan Tull <atull@xxxxxxxxxx>
Cc: Moritz Fischer <mdf@xxxxxxxxxx>
Cc: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
Cc: linux-fpga@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Reviewed-by: Moritz Fischer <mdf@xxxxxxxxxx>
Reviewed-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
Acked-by: Alan Tull <atull@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/fpga/stratix10-soc.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/fpga/stratix10-soc.c b/drivers/fpga/stratix10-soc.c
index 13851b3d1c56..215d33789c74 100644
--- a/drivers/fpga/stratix10-soc.c
+++ b/drivers/fpga/stratix10-soc.c
@@ -507,12 +507,16 @@ static int __init s10_init(void)
if (!fw_np)
return -ENODEV;

+ of_node_get(fw_np);
np = of_find_matching_node(fw_np, s10_of_match);
- if (!np)
+ if (!np) {
+ of_node_put(fw_np);
return -ENODEV;
+ }

ret = of_platform_populate(fw_np, s10_of_match, NULL, NULL);
+ of_node_put(fw_np);
if (ret)
return ret;