linux-kernel - [PATCH] watchdog/perf: Optimize bytes copied and remove manual NUL-termination

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Message-ID: <20250313133004.36406-2-thorsten.blum@linux.dev>
Date: Thu, 13 Mar 2025 14:30:02 +0100
From: Thorsten Blum <thorsten.blum@...ux.dev>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Song Liu <song@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Thorsten Blum <thorsten.blum@...ux.dev>
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH] watchdog/perf: Optimize bytes copied and remove manual NUL-termination

Currently, up to 23 bytes of the source string are copied to the
destination buffer (including the comma and anything after it), only to
then manually NUL-terminate the destination buffer again at index 'len'
(where the comma was found).

Fix this by calling strscpy() with 'len' instead of the destination
buffer size to copy only as many bytes from the source string as needed.

Change the length check to allow 'len' to be less than or equal to the
destination buffer size to fill the whole buffer if needed.

Remove the if-check for the return value of strscpy(), because calling
strscpy() with 'len' always truncates the source string at the comma as
expected and NUL-terminates the destination buffer at the corresponding
index instead. Remove the manual NUL-termination.

No functional changes intended.

Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
---
 kernel/watchdog_perf.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/watchdog_perf.c b/kernel/watchdog_perf.c
index 59c1d86a73a2..b81167cb0dfc 100644
--- a/kernel/watchdog_perf.c
+++ b/kernel/watchdog_perf.c
@@ -294,12 +294,10 @@ void __init hardlockup_config_perf_event(const char *str)
 	} else {
 		unsigned int len = comma - str;

-		if (len >= sizeof(buf))
+		if (len > sizeof(buf))
 			return;

-		if (strscpy(buf, str, sizeof(buf)) < 0)
-			return;
-		buf[len] = 0;
+		strscpy(buf, str, len);
 		if (kstrtoull(buf, 16, &config))
 			return;
 	}
-- 
2.48.1