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From: Alexey Dobriyan <adobriyan@gmail.com>
To: akpm@osdl.org
Subject: Re: potential-null-pointer-dereference-in-amiga-serial-driver.patch added to -mm tree
Date: Tue, 31 May 2005 19:49:15 +0400
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Cc: julien.tinnes@francetelecom.com, linux-kernel@vger.kernel.org
References: <200505310909.j4V98xBR008727@shell0.pdx.osdl.net>
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On Tuesday 31 May 2005 13:08, akpm@osdl.org wrote:
> A pointer is dereferenced before it is null-checked.

> --- 25/drivers/char/amiserial.c~potential-null-pointer-dereference-in-amiga-serial-driver
> +++ 25-akpm/drivers/char/amiserial.c

>  static void rs_put_char(struct tty_struct *tty, unsigned char ch)
>  {
> -	struct async_struct *info = (struct async_struct *)tty->driver_data;
> +	struct async_struct *info;
>  	unsigned long flags;
>  
> +	if (!tty)
> +		return;

Can ->put_char be ever called with tty being NULL? From my reading of
drivers/char/n_tty.c it can't.

Every single time ->put_char is used a-la

	tty->driver->put_char(tty, '\r');

So, tty will be dereferenced before function call. Same for static inline
put_char() there.

> +
> +	info = tty->driver_data;

>  static int rs_write(struct tty_struct * tty, const unsigned char *buf, int count)
>  {

> -	struct async_struct *info = (struct async_struct *)tty->driver_data;
> +	struct async_struct *info;
>  	unsigned long flags;
>  
> +	if (!tty)
> +		return 0;

Same question.

> +
> +	info = tty->driver_data;
-
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