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.

Link: https://lore.kernel.org/r/20200522065306.83-1-shreyas.joshi@biamp.com
Signed-off-by: Shreyas Joshi <shreyas.joshi@biamp.com>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
[pmladek@suse.com: Better format the commit message and code, remove unnecessary brackets.]
Signed-off-by: Petr Mladek <pmladek@suse.com>

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 35cc5f5..a399050 100644 (file)
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2200,6 +2200,9 @@ 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;