linux-kernel - [PATCH net-next 9/9] net: netconsole: Fix a wrong warning

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Message-ID: <20240903140757.2802765-10-leitao@debian.org>
Date: Tue,  3 Sep 2024 07:07:52 -0700
From: Breno Leitao <leitao@...ian.org>
To: kuba@...nel.org,
	davem@...emloft.net,
	edumazet@...gle.com,
	pabeni@...hat.com,
	Matthew Wood <thepacketgeek@...il.com>
Cc: horms@...nel.org,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	davej@...emonkey.org.uk,
	thevlad@...a.com,
	max@...sevol.com
Subject: [PATCH net-next 9/9] net: netconsole: Fix a wrong warning

A warning is triggered when there is insufficient space in the buffer
for userdata. However, this is not an issue since userdata will be sent
in the next iteration.

Current warning message:

    ------------[ cut here ]------------
     WARNING: CPU: 13 PID: 3013042 at drivers/net/netconsole.c:1122 write_ext_msg+0x3b6/0x3d0
      ? write_ext_msg+0x3b6/0x3d0
      console_flush_all+0x1e9/0x330

The code incorrectly issues a warning when this_chunk is zero, which is
a valid scenario. The warning should only be triggered when this_chunk
is negative.

Signed-off-by: Breno Leitao <leitao@...ian.org>
Fixes: 1ec9daf95093 ("net: netconsole: append userdata to fragmented netconsole messages")
---
 drivers/net/netconsole.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 81d7d2b09988..83662a28dc00 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -1124,8 +1124,13 @@ static void send_fragmented_body(struct netconsole_target *nt, char *buf,
 
 			this_chunk = min(userdata_len - sent_userdata,
 					 MAX_PRINT_CHUNK - preceding_bytes);
-			if (WARN_ON_ONCE(this_chunk <= 0))
+			if (WARN_ON_ONCE(this_chunk < 0))
+				/* this_chunk could be zero if all the previous message used
+				 * all the buffer. This is not a problem, userdata will be sent
+				 * in the next iteration
+				 */
 				return;
+
 			memcpy(buf + this_header + this_offset,
 			       userdata + sent_userdata,
 			       this_chunk);
-- 
2.43.5