[PATCH] MIPS: fw: Allow firmware to pass a empty env

[Jiaxun Yang]

fw_getenv will use env entry to determine style of env,
however it is legal for firmware to just pass a empty list.

Check if first entry exist before running strchr to avoid
null pointer dereference.

Cc: stable@xxxxxxxxxxxxxxx
Link: https://github.com/clbr/n64bootloader/issues/5
Signed-off-by: Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx>
---
Note: Fixes tag is intentionally omitted for this patch, although
the booting issue only comes in 6.1, the logic issue is been since very start.
---
 arch/mips/fw/lib/cmdline.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/fw/lib/cmdline.c b/arch/mips/fw/lib/cmdline.c
index f24cbb4a39b5..892765b742bb 100644
--- a/arch/mips/fw/lib/cmdline.c
+++ b/arch/mips/fw/lib/cmdline.c
@@ -53,7 +53,7 @@ char *fw_getenv(char *envname)
 {
 	char *result = NULL;
 
-	if (_fw_envp != NULL) {
+	if (_fw_envp != NULL && fw_envp(0) != NULL) {
 		/*
 		 * Return a pointer to the given environment variable.
 		 * YAMON uses "name", "value" pairs, while U-Boot uses
-- 
2.39.2 (Apple Git-143)