linux-kernel - Re: [PATCH -tip] x86: uv - prevent NULL dereference in uv_system

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Message-ID: <20090503084847.GA20394@elte.hu>
Date:	Sun, 3 May 2009 10:48:47 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jack Steiner <steiner@....com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Cyrill Gorcunov <gorcunov@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -tip] x86: uv - prevent NULL dereference in
	uv_system_init


* Jack Steiner <steiner@....com> wrote:

> >  arch/x86/kernel/apic/x2apic_uv_x.c |    3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > Index: linux-2.6.git/arch/x86/kernel/apic/x2apic_uv_x.c
> > =====================================================================
> > --- linux-2.6.git.orig/arch/x86/kernel/apic/x2apic_uv_x.c
> > +++ linux-2.6.git/arch/x86/kernel/apic/x2apic_uv_x.c
> > @@ -584,15 +584,18 @@ void __init uv_system_init(void)
> >  
> >  	bytes = sizeof(struct uv_blade_info) * uv_num_possible_blades();
> >  	uv_blade_info = kmalloc(bytes, GFP_KERNEL);
> > +	BUG_ON(!uv_blade_info);
> >  
> >  	get_lowmem_redirect(&lowmem_redir_base, &lowmem_redir_size);
> >  
> >  	bytes = sizeof(uv_node_to_blade[0]) * num_possible_nodes();
> >  	uv_node_to_blade = kmalloc(bytes, GFP_KERNEL);
> > +	BUG_ON(!uv_node_to_blade);
> >  	memset(uv_node_to_blade, 255, bytes);
> >  
> >  	bytes = sizeof(uv_cpu_to_blade[0]) * num_possible_cpus();
> >  	uv_cpu_to_blade = kmalloc(bytes, GFP_KERNEL);
> > +	BUG_ON(!uv_cpu_to_blade);
> >  	memset(uv_cpu_to_blade, 255, bytes);

Hm, would be nice if we had a __GFP_PANIC variant in kmalloc that 
would just panic straight in the allocator, when allocation failure 
is not acceptable. (Andrew Cc:-ed)

It does not increase the priority of the allocation nor does it 
trigger any 'dont fail' logic - it is simply the central expression 
of 'this should not have failed, panic'.

Thus we'd avoid all these duplicated BUG_ON() places.

	Ingo
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