netdev - [PATCH net-next 1/3] net: sysctl: remove always-true condition

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Message-ID: <20241017152422.487406-2-atenart@kernel.org>
Date: Thu, 17 Oct 2024 17:24:17 +0200
From: Antoine Tenart <atenart@...nel.org>
To: davem@...emloft.net,
	kuba@...nel.org,
	pabeni@...hat.com,
	edumazet@...gle.com
Cc: Antoine Tenart <atenart@...nel.org>,
	netdev@...r.kernel.org
Subject: [PATCH net-next 1/3] net: sysctl: remove always-true condition

Before adding a new line at the end of the temporary buffer in
dump_cpumask, a length check is performed to ensure there is space for
it.

  len = min(sizeof(kbuf) - 1, *lenp);
  len = scnprintf(kbuf, len, ...);
  if (len < *lenp)
          kbuf[len++] = '\n';

Note that the check is currently logically wrong, the written length is
compared against the output buffer, not the temporary one. However this
has no consequence as this is always true, even if fixed: scnprintf
includes a null char at the end of the buffer but the returned length do
not include it and there is always space for overriding it with a
newline.

Remove the condition.

Signed-off-by: Antoine Tenart <atenart@...nel.org>
---
 net/core/sysctl_net_core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index b60fac380cec..e7c0121dfaa1 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -69,8 +69,10 @@ static void dump_cpumask(void *buffer, size_t *lenp, loff_t *ppos,
 		return;
 	}

-	if (len < *lenp)
-		kbuf[len++] = '\n';
+	/* scnprintf writes a trailing null char not counted in the returned
+	 * length, override it with a newline.
+	 */
+	kbuf[len++] = '\n';
 	memcpy(buffer, kbuf, len);
 	*lenp = len;
 	*ppos += len;
-- 
2.47.0