linux-kernel - [PATCH v2 4/4] soc: apple: rtkit: Cut syslog messages after the first '\0'

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Message-Id: <20250226-apple-soc-misc-v2-4-c3ec37f9021b@svenpeter.dev>
Date: Wed, 26 Feb 2025 19:00:06 +0000
From: Sven Peter via B4 Relay <devnull+sven.svenpeter.dev@...nel.org>
To: Alyssa Rosenzweig <alyssa@...enzweig.io>, Janne Grunau <j@...nau.net>, 
 Sven Peter <sven@...npeter.dev>
Cc: asahi@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
 linux-kernel@...r.kernel.org
Subject: [PATCH v2 4/4] soc: apple: rtkit: Cut syslog messages after the
 first '\0'

From: Janne Grunau <j@...nau.net>

Certain messages from DCP contain NUL bytes in the random data after the
NUL terminated syslog message. Since the syslog message ends with '\n'
this results in a dev_info() message terminated with two newlines and an
empty printed line in the kernel log.

Signed-off-by: Janne Grunau <j@...nau.net>
Reviewed-by: Alyssa Rosenzweig <alyssa@...enzweig.io>
Signed-off-by: Sven Peter <sven@...npeter.dev>
---
 drivers/soc/apple/rtkit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/soc/apple/rtkit.c b/drivers/soc/apple/rtkit.c
index 4b78463dd5a1..5fffd0f003dc 100644
--- a/drivers/soc/apple/rtkit.c
+++ b/drivers/soc/apple/rtkit.c
@@ -477,7 +477,7 @@ static void apple_rtkit_syslog_rx_log(struct apple_rtkit *rtk, u64 msg)
 
 	log_context[sizeof(log_context) - 1] = 0;
 
-	msglen = rtk->syslog_msg_size - 1;
+	msglen = strnlen(rtk->syslog_msg_buffer, rtk->syslog_msg_size - 1);
 	while (msglen > 0 &&
 		   should_crop_syslog_char(rtk->syslog_msg_buffer[msglen - 1]))
 		msglen--;

-- 
2.34.1