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From:   Jiaxun Yang <jiaxun.yang@flygoat.com>
To:     linux-mips@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, tsbogend@alpha.franken.de,
        and@gmx.com, Jiaxun Yang <jiaxun.yang@flygoat.com>,
        stable@vger.kernel.org
Subject: [PATCH] MIPS: fw: Allow firmware to pass a empty env
Date:   Tue, 11 Apr 2023 12:14:26 +0100
Message-Id: <20230411111426.55889-1-jiaxun.yang@flygoat.com>
MIME-Version: 1.0
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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@vger.kernel.org
Link: https://github.com/clbr/n64bootloader/issues/5
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
---
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)