linux-kernel - [PATCH] printk: handle blank console arguments passed in.

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Message-ID: <MN2PR17MB31979437E605257461AC003DFCF60@MN2PR17MB3197.namprd17.prod.outlook.com>
Date:   Tue, 17 Mar 2020 01:34:43 +0000
From:   Shreyas Joshi <Shreyas.Joshi@...mp.com>
To:     Shreyas Joshi <Shreyas.Joshi@...mp.com>,
        "pmladek@...e.com" <pmladek@...e.com>,
        "sergey.senozhatsky@...il.com" <sergey.senozhatsky@...il.com>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "shreyasjoshi15@...il.com" <shreyasjoshi15@...il.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] printk: handle blank console arguments passed in.

If uboot passes a blank string to console_setup then it results in a trashed memory.
Ultimately, the kernel crashes during freeing up the memory. This fix checks if there is a blank parameter being passed to console_setup from uboot.
In case it detects that the console parameter is blank then it doesn't setup the serial device and it gracefully exits.

Signed-off-by: Shreyas Joshi <shreyas.joshi@...mp.com>
---
 kernel/printk/printk.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index ad4606234545..e9ad730991e0 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2165,7 +2165,10 @@ static int __init console_setup(char *str)
 	char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
 	char *s, *options, *brl_options = NULL;
 	int idx;
-
+	if (str[0] == 0) {
+		console_loglevel = 0;
+		return 1;
+	}
 	if (_braille_console_setup(&str, &brl_options))
 		return 1;
 
--
2.20.1