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

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Date:   Fri, 22 May 2020 16:40:29 +1000
From:   Shreyas Joshi <shreyas.joshi@...mp.com>
To:     sergey.senozhatsky@...il.com, rostedt@...dmis.org,
        pmladek@...e.com, shreyasjoshi15@...il.com
CC:     linux-kernel@...r.kernel.org,
        Shreyas Joshi <shreyas.joshi@...mp.com>
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>
---
 V1:
    Fixed console_loglevel to default as per the review comments

 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) {
+		return 1;
+	}
 	if (_braille_console_setup(&str, &brl_options))
 		return 1;
 
-- 
2.20.1