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

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Date:	Sun, 3 May 2009 13:01:10 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Jack Steiner <steiner@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH -tip] x86: uv - prevent NULL dereference in
	uv_system_init

[Ingo Molnar - Sun, May 03, 2009 at 10:48:47AM +0200]
| 
| * 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
| 

Yes, we have SLAB_PANIC, the similar (in behaviour) could be
done for kmalloc. (Pekka and Rik CC'ed as well)

	-- Cyrill
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