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Date:   Tue, 6 Oct 2020 11:59:35 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To:     Petr Mladek <pmladek@suse.com>
Cc:     Shreyas Joshi <shreyas.joshi@biamp.com>,
        sergey.senozhatsky@gmail.com, rostedt@goodmis.org,
        shreyasjoshi15@gmail.com, linux-kernel@vger.kernel.org,
        Guenter Roeck <linux@roeck-us.net>
Subject: Re: [PATCH] printk: handle blank console arguments passed in.
Message-ID: <20201006025935.GA597@jagdpanzerIV.localdomain>
References: <MN2PR17MB31979437E605257461AC003DFCF60@MN2PR17MB3197.namprd17.prod.outlook.com>
 <20200522065306.83-1-shreyas.joshi@biamp.com>
 <20200522100046.GH3464@linux-b0ei>
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Cc-ing Guenter,

On (20/05/22 12:00), Petr Mladek wrote:
> On Fri 2020-05-22 16:53:06, Shreyas Joshi wrote:
> > 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@biamp.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;
> 
> I have fixed formatting and pushed it into printk/linux.git,
> branch for-5.8.

Petr, this patch's causing regressions for us. We use blank console= boot
param to bypass dts. It appears that it'd be better to revert the change.

	-ss