Re: [patch 1/5] x86: ACPI - add checking for NULL early param

[Cyrill Gorcunov <gorcunov@gmail.com>]

[Andrew Morton - Tue, Jul 22, 2008 at 02:53:32AM -0700]
| On Sat, 05 Jul 2008 15:53:35 +0400 Cyrill Gorcunov <gorcunov@gmail.com> wrote:
| 
| > Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
| > ---
| > 
| > Index: linux-2.6.git/drivers/acpi/tables.c
| > ====================================================================
| > --- linux-2.6.git.orig/drivers/acpi/tables.c	2008-01-21 23:14:47.000000000 +0300
| > +++ linux-2.6.git/drivers/acpi/tables.c	2008-07-05 12:24:16.000000000 +0400
| > @@ -300,6 +300,8 @@ int __init acpi_table_init(void)
| >  
| >  static int __init acpi_parse_apic_instance(char *str)
| >  {
| > +	if (!str)
| > +		return -EINVAL;
| >  
| >  	acpi_apic_instance = simple_strtoul(str, NULL, 0);
| >  
| 
| Could you please explain this patch?
| 

we could get NULL deref here - if you start kernel as

	qemu-system-x86_64 -kernel arch/x86/boot/bzImage -append "root=/dev/sda acpi_apic_instance" ../images/root-j

so user was not carried about correct boot option and the kernel respond by
hang - which is not good I think. Actually - by the patch we easy protect
ourself from user-madness :)

		- Cyrill -