Re: [PATCH -tip] x86: uv - prevent NULL dereference in uv_system_init

Jack Steiner
2009-05-01T20:31:38Z

On Sat, May 02, 2009 at 12:25:11AM +0400, Cyrill Gorcunov wrote:
> [Cyrill Gorcunov - Sat, May 02, 2009 at 12:09:37AM +0400]
> | [Ingo Molnar - Fri, May 01, 2009 at 10:03:31PM +0200]
> | |
> | | * Cyrill Gorcunov <gorcunov@openvz.org> wrote:
> | |
> | | > We may reach NULL dereference oops if kmalloc failed.
> | | > Lets do panic better with sensible message.
> | | >
> | | > Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
> | | > ---
> | | >
> | | > Actually there is a dubious place as well at early_get_nodeid.
> | | > Is there a guarantee that we _never_ fail in early_ioremap?
> | | >
> | | > arch/x86/kernel/apic/x2apic_uv_x.c | 9 +++++++++
> | | > 1 file changed, 9 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 +584,21 @@ void __init uv_system_init(void)
> | | >
> | | > bytes = sizeof(struct uv_blade_info) * uv_num_possible_blades();
> | | > uv_blade_info = kmalloc(bytes, GFP_KERNEL);
> | | > + if (!uv_blade_info)
> | | > + goto err_nomem;
> | |
> | | hm, i think a BUG_ON() might be shorter and more appropriate here.
> | | We really shouldnt be running out of memory during system init.
> | |
> | | Ingo
> | |
> |
> | Yeah, indeed! I was thinking of __GPF_NOFAIL here as well with
> | message on top like pr_debug("UV: allocating memory\n") or something
> | like that. It would make it even cleaner I guess. Hmm?
> |
> | -- Cyrill
>
> Here is an updated one.

Acked-by: Jack Steiner <steiner@sgi.com>

>
> -- Cyrill
> ---
> From: Cyrill Gorcunov <gorcunov@openvz.org>
> Subject: [PATCH -tip] x86: uv - prevent NULL dereference in uv_system_init
>
> We may reach NULL dereference oops if kmalloc failed.
> Prevent it with explisit BUG_ON.
>
> Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
> ---
> 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);
>
> blade = 0;