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

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Message-ID: <20201006025935.GA597@jagdpanzerIV.localdomain>
Date:   Tue, 6 Oct 2020 11:59:35 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Shreyas Joshi <shreyas.joshi@...mp.com>,
        sergey.senozhatsky@...il.com, rostedt@...dmis.org,
        shreyasjoshi15@...il.com, linux-kernel@...r.kernel.org,
        Guenter Roeck <linux@...ck-us.net>
Subject: Re: [PATCH] printk: handle blank console arguments passed in.

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@...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;
> 
> 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