[PATCH 1/4] fpga: stratix10-soc: fix use-after-free on s10_init()

From: Alan Tull
Date: Thu May 09 2019 - 17:09:55 EST

From: Wen Yang <wen.yang99@xxxxxxxxxx>

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>
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;