[PATCH v2025.09.y 44/49] 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>
Link: https://lore.barebox.org/20251211171706.2369329-1-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
(cherry picked from commit c8cfce813f2f7e5df84bf2ba4364212c04102451)
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 274e6fcb8376..770c90ec48b4 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