linux-kernel - [PATCH] sparc/led: prevent buffer underflow on zero-length write

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Message-Id: <20251030072156.30656-1-linmq006@gmail.com>
Date: Thu, 30 Oct 2025 15:21:53 +0800
From: Miaoqian Lin <linmq006@...il.com>
To: "David S. Miller" <davem@...emloft.net>,
	Andreas Larsson <andreas@...sler.com>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Lars Kotthoff <metalhead@...alhead.ws>,
	sparclinux@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: linmq006@...il.com,
	stable@...r.kernel.org
Subject: [PATCH] sparc/led: prevent buffer underflow on zero-length write

Fix out-of-bounds access in led_proc_write() when count is 0.
Accessing buf[count - 1] with count=0 reads/writes buf[-1].

Check for count==0 and return -EINVAL early to fix this.

Found via static analysis and code review.

Fixes: ee1858d3122d ("[SPARC]: Add sun4m LED driver.")
Cc: stable@...r.kernel.org
Signed-off-by: Miaoqian Lin <linmq006@...il.com>
---
 arch/sparc/kernel/led.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/sparc/kernel/led.c b/arch/sparc/kernel/led.c
index f4fb82b019bb..aa0ca0d8d0e2 100644
--- a/arch/sparc/kernel/led.c
+++ b/arch/sparc/kernel/led.c
@@ -70,6 +70,9 @@ static ssize_t led_proc_write(struct file *file, const char __user *buffer,
 {
 	char *buf = NULL;
 
+	if (count == 0)
+		return -EINVAL;
+
 	if (count > LED_MAX_LENGTH)
 		count = LED_MAX_LENGTH;
 
-- 
2.39.5 (Apple Git-154)