[PATCH 4.9 090/121] printk: handle blank console arguments passed in.

[Greg Kroah-Hartman]

From: Shreyas Joshi <shreyas.joshi@xxxxxxxxx>

[ Upstream commit 48021f98130880dd74286459a1ef48b5e9bc374f ]

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.

Link: https://lore.kernel.org/r/20200522065306.83-1-shreyas.joshi@xxxxxxxxx
Signed-off-by: Shreyas Joshi <shreyas.joshi@xxxxxxxxx>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
[pmladek@xxxxxxxx: Better format the commit message and code, remove unnecessary brackets.]
Signed-off-by: Petr Mladek <pmladek@xxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 kernel/printk/printk.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index c1873d325ebda..7acae2f2478d9 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2035,6 +2035,9 @@ static int __init console_setup(char *str)
 	char *s, *options, *brl_options = NULL;
 	int idx;
 
+	if (str[0] == 0)
+		return 1;
+
 	if (_braille_console_setup(&str, &brl_options))
 		return 1;
 
-- 
2.25.1