linux-kernel - [PATCH] printk: fix string termination for record_print

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Date:   Sun, 24 Jan 2021 21:33:28 +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>,
        Sven Schnelle <svens@...ux.ibm.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] printk: fix string termination for record_print_text()

Commit f0e386ee0c0b ("printk: fix buffer overflow potential for
print_text()") added string termination in record_print_text().
However it used the wrong base pointer for adding the terminator.
This led to a 0-byte being written somewhere beyond the buffer.

Use the correct base pointer when adding the terminator.

Fixes: f0e386ee0c0b ("printk: fix buffer overflow potential for print_text()")
Reported-by: Sven Schnelle <svens@...ux.ibm.com>
Signed-off-by: John Ogness <john.ogness@...utronix.de>
---
 kernel/printk/printk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 6639a0cfe0ac..5a95c688621f 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1398,7 +1398,7 @@ static size_t record_print_text(struct printk_record *r, bool syslog,
 	 * not counted in the return value.
 	 */
 	if (buf_size > 0)
-		text[len] = 0;
+		r->text_buf[len] = 0;
 
 	return len;
 }
-- 
2.20.1