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

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Message-ID: <20201007143921.GA470@jagdpanzerIV.localdomain>
Date:   Wed, 7 Oct 2020 23:39:21 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Shreyas Joshi <shreyas.joshi@...mp.com>, rostedt@...dmis.org,
        shreyasjoshi15@...il.com, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [PATCH] printk: handle blank console arguments passed in.

On (20/10/07 21:30), Sergey Senozhatsky wrote:
> On (20/10/07 09:28), Petr Mladek wrote:
> > 
> > 		/*
> > 		 * Dirty hack to prevent using any console with tty
> > 		 * binding as a fallback and adding the empty
> > 		 * name into console_cmdline array.
> > 		 */
> > 		preferred_console = MAX_CMDLINECONSOLES;
[..]
> Hint: I can crash my laptop when I remove the "console=" boot param and
> comment out init_dup(file) calls in console_on_rootfs().

My guess is that since we don't have stdin/out/err fds then,
theoretically, something like this can happen

int main()
{
...
	int fd = open(.... );
	int fd = open(..., "vfat.ko");

	//fd is 1

	fprintf(stdout, "loading vfat\n");
...
}

stdout (fd 1) is not stdout, it's fd that we got from open(vfat.ko).

Does this make sense?

	-ss