linux-kernel - [PATCH] printk: finalize records with trailing newlines

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Date:   Thu, 26 Nov 2020 12:54:36 +0106
From:   John Ogness <john.ogness@...utronix.de>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Atish Patra <atishp@...shpatra.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] printk: finalize records with trailing newlines

Any record with a trailing newline (LOG_NEWLINE flag) cannot
be continued because the newline has been stripped and will
not be visible if the message is appended. This was already
handled correctly when committing in log_output() but was
not handled correctly when committing in log_store().

Fixes: f5f022e53b87 ("printk: reimplement log_cont using record extension")
Signed-off-by: John Ogness <john.ogness@...utronix.de>
---
 This is an important bugfix for continuous messages and should
 be part of the 5.10 release.

 If not applied, newlines will vanish when concatenating
 continuous with trailing newlines.

 kernel/printk/printk.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index fe64a49344bf..bc1e3b5a97bd 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -528,8 +528,8 @@ static int log_store(u32 caller_id, int facility, int level,
 	if (dev_info)
 		memcpy(&r.info->dev_info, dev_info, sizeof(r.info->dev_info));
 
-	/* insert message */
-	if ((flags & LOG_CONT) || !(flags & LOG_NEWLINE))
+	/* A message without a trailing newline can be continued. */
+	if (!(flags & LOG_NEWLINE))
 		prb_commit(&e);
 	else
 		prb_final_commit(&e);
-- 
2.20.1