[PATCH master] param: make setting a parameter to the same string value a no-op

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

setenv("global.bootm.root_param", getenv("global.bootm.root_param"))
triggers a use-after-free, because the value is free'd before being
duplicated and allocated again.

Let's just early exit in this case as there's nothing further to do.

This was noticed by KASAN when bootm_data_restore_defaults restored
global.bootm.root_param.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 lib/parameter.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/parameter.c b/lib/parameter.c
index b9a449c32657..bf5dbbb05e6b 100644
--- a/lib/parameter.c
+++ b/lib/parameter.c
@@ -131,6 +131,8 @@ int bobject_set_param(bobject_t _bobj, const char *name, const char *val)
 int bobject_param_set_generic(bobject_t _bobj, struct param_d *p,
 			  const char *val)
 {
+	if (val == p->value)
+		return 0;
 	free(p->value);
 	if (!val) {
 		p->value = NULL;
-- 
2.47.3