[PATCH 3.3.0-rc3] Fix use-after-free in acpi_map_lsapic

[PATCH 3.3.0-rc3] Fix use-after-free in acpi_map_lsapic

[Petr Vandrovec]

From: Petr Vandrovec <petr@vmware.com>

When processor is being hot-added to the system, acpi_map_lsapic invokes
ACPI _MAT method to find APIC ID and flags, verifies that returned structure
is indeed ACPI's local APIC structure, and that flags contain MADT_ENABLED
bit.  Then saves APIC ID, frees structure - and accesses structure when
computing arguments for acpi_register_lapic call.  Which sometime leads
to acpi_register_lapic call being made with second argument zero, failing
to bring processor online with error 'Unable to map lapic to logical cpu
number'.

As lapic->lapic_flags & ACPI_MADT_ENABLED was already confirmed to be non-zero
few lines above, we can just pass unconditional ACPI_MADT_ENABLED to the
acpi_register_lapic.

Thanks, Petr

Signed-off-by: Petr Vandrovec <petr@vmware.com>
Signed-off-by: Alok Kataria <akataria@vmware.com>


diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index ce664f3..a4a0901 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -650,7 +650,7 @@ static int __cpuinit _acpi_map_lsapic(acpi_handle handle, int *pcpu)
 		goto free_tmp_map;
 
 	cpumask_copy(tmp_map, cpu_present_mask);
-	acpi_register_lapic(physid, lapic->lapic_flags & ACPI_MADT_ENABLED);
+	acpi_register_lapic(physid, ACPI_MADT_ENABLED);
 
 	/*
 	 * If mp_register_lapic successfully generates a new logical cpu

Re: [PATCH 3.3.0-rc3] Fix use-after-free in acpi_map_lsapic

[Alok Kataria]

Len, anyone else, 

Any comments on this one ? This fixes a important bug during cpu hotadd
where the kernel fails to recognize all the newly added cpus.

Thanks,
Alok


On Wed, 2012-02-15 at 16:06 -0800, Petr Vandrovec wrote:
> From: Petr Vandrovec <petr@vmware.com>
> 
> When processor is being hot-added to the system, acpi_map_lsapic invokes
> ACPI _MAT method to find APIC ID and flags, verifies that returned structure
> is indeed ACPI's local APIC structure, and that flags contain MADT_ENABLED
> bit.  Then saves APIC ID, frees structure - and accesses structure when
> computing arguments for acpi_register_lapic call.  Which sometime leads
> to acpi_register_lapic call being made with second argument zero, failing
> to bring processor online with error 'Unable to map lapic to logical cpu
> number'.
> 
> As lapic->lapic_flags & ACPI_MADT_ENABLED was already confirmed to be non-zero
> few lines above, we can just pass unconditional ACPI_MADT_ENABLED to the
> acpi_register_lapic.
> 
> Thanks, Petr
> 
> Signed-off-by: Petr Vandrovec <petr@vmware.com>
> Signed-off-by: Alok Kataria <akataria@vmware.com>
> 
> 
> diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
> index ce664f3..a4a0901 100644
> --- a/arch/x86/kernel/acpi/boot.c
> +++ b/arch/x86/kernel/acpi/boot.c
> @@ -650,7 +650,7 @@ static int __cpuinit _acpi_map_lsapic(acpi_handle handle, int *pcpu)
>  		goto free_tmp_map;
>  
>  	cpumask_copy(tmp_map, cpu_present_mask);
> -	acpi_register_lapic(physid, lapic->lapic_flags & ACPI_MADT_ENABLED);
> +	acpi_register_lapic(physid, ACPI_MADT_ENABLED);
>  
>  	/*
>  	 * If mp_register_lapic successfully generates a new logical cpu

Re: [PATCH 3.3.0-rc3] Fix use-after-free in acpi_map_lsapic

[Toshi Kani]

On Wed, 2012-03-07 at 11:48 -0800, Alok Kataria wrote:
> Len, anyone else, 
> 
> Any comments on this one ? This fixes a important bug during cpu hotadd
> where the kernel fails to recognize all the newly added cpus.
> 
> Thanks,
> Alok
> 
> 
> On Wed, 2012-02-15 at 16:06 -0800, Petr Vandrovec wrote:
> > From: Petr Vandrovec <petr@vmware.com>
> > 
> > When processor is being hot-added to the system, acpi_map_lsapic invokes
> > ACPI _MAT method to find APIC ID and flags, verifies that returned structure
> > is indeed ACPI's local APIC structure, and that flags contain MADT_ENABLED
> > bit.  Then saves APIC ID, frees structure - and accesses structure when
> > computing arguments for acpi_register_lapic call.  Which sometime leads
> > to acpi_register_lapic call being made with second argument zero, failing
> > to bring processor online with error 'Unable to map lapic to logical cpu
> > number'.
> > 
> > As lapic->lapic_flags & ACPI_MADT_ENABLED was already confirmed to be non-zero
> > few lines above, we can just pass unconditional ACPI_MADT_ENABLED to the
> > acpi_register_lapic.
> > 
> > Thanks, Petr
> > 
> > Signed-off-by: Petr Vandrovec <petr@vmware.com>
> > Signed-off-by: Alok Kataria <akataria@vmware.com>
> > 
> > 
> > diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
> > index ce664f3..a4a0901 100644
> > --- a/arch/x86/kernel/acpi/boot.c
> > +++ b/arch/x86/kernel/acpi/boot.c
> > @@ -650,7 +650,7 @@ static int __cpuinit _acpi_map_lsapic(acpi_handle handle, int *pcpu)
> >  		goto free_tmp_map;
> >  
> >  	cpumask_copy(tmp_map, cpu_present_mask);
> > -	acpi_register_lapic(physid, lapic->lapic_flags & ACPI_MADT_ENABLED);
> > +	acpi_register_lapic(physid, ACPI_MADT_ENABLED);

The change looks good. I suggest you also add the following line to
prevent such bug in future.

        kfree(buffer.pointer);
        buffer.length = ACPI_ALLOCATE_BUFFER;
        buffer.pointer = NULL;
+       lapic = NULL;

Thanks,
-Toshi


> >  
> >  	/*
> >  	 * If mp_register_lapic successfully generates a new logical cpu
> 
> --
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Re: [PATCH 3.3.0-rc3] Fix use-after-free in acpi_map_lsapic

[Alok Kataria]

Hi Toshi, 

On Thu, 2012-03-08 at 14:01 -0700, Toshi Kani wrote:
> On Wed, 2012-03-07 at 11:48 -0800, Alok Kataria wrote:
> > Len, anyone else, 
> > 
> > Any comments on this one ? This fixes a important bug during cpu hotadd
> > where the kernel fails to recognize all the newly added cpus.
> > 
> > Thanks,
> > Alok
> > 
> > 
> > On Wed, 2012-02-15 at 16:06 -0800, Petr Vandrovec wrote:
> > > From: Petr Vandrovec <petr@vmware.com>
> > > 
> > > When processor is being hot-added to the system, acpi_map_lsapic invokes
> > > ACPI _MAT method to find APIC ID and flags, verifies that returned structure
> > > is indeed ACPI's local APIC structure, and that flags contain MADT_ENABLED
> > > bit.  Then saves APIC ID, frees structure - and accesses structure when
> > > computing arguments for acpi_register_lapic call.  Which sometime leads
> > > to acpi_register_lapic call being made with second argument zero, failing
> > > to bring processor online with error 'Unable to map lapic to logical cpu
> > > number'.
> > > 
> > > As lapic->lapic_flags & ACPI_MADT_ENABLED was already confirmed to be non-zero
> > > few lines above, we can just pass unconditional ACPI_MADT_ENABLED to the
> > > acpi_register_lapic.
> > > 
> > > Thanks, Petr
> > > 
> > > Signed-off-by: Petr Vandrovec <petr@vmware.com>
> > > Signed-off-by: Alok Kataria <akataria@vmware.com>
> > > 
> > > 
> > > diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
> > > index ce664f3..a4a0901 100644
> > > --- a/arch/x86/kernel/acpi/boot.c
> > > +++ b/arch/x86/kernel/acpi/boot.c
> > > @@ -650,7 +650,7 @@ static int __cpuinit _acpi_map_lsapic(acpi_handle handle, int *pcpu)
> > >  		goto free_tmp_map;
> > >  
> > >  	cpumask_copy(tmp_map, cpu_present_mask);
> > > -	acpi_register_lapic(physid, lapic->lapic_flags & ACPI_MADT_ENABLED);
> > > +	acpi_register_lapic(physid, ACPI_MADT_ENABLED);
> 
> The change looks good. I suggest you also add the following line to
> prevent such bug in future.
> 
>         kfree(buffer.pointer);
>         buffer.length = ACPI_ALLOCATE_BUFFER;
>         buffer.pointer = NULL;
> +       lapic = NULL;

That's a good suggestion, below is the updated patch. Thanks !!
--

From: Petr Vandrovec <petr@vmware.com>

When processor is being hot-added to the system, acpi_map_lsapic invokes
ACPI _MAT method to find APIC ID and flags, verifies that returned structure
is indeed ACPI's local APIC structure, and that flags contain MADT_ENABLED
bit.  Then saves APIC ID, frees structure - and accesses structure when
computing arguments for acpi_register_lapic call.  Which sometime leads
to acpi_register_lapic call being made with second argument zero, failing
to bring processor online with error 'Unable to map lapic to logical cpu
number'.

As lapic->lapic_flags & ACPI_MADT_ENABLED was already confirmed to be non-zero
few lines above, we can just pass unconditional ACPI_MADT_ENABLED to the
acpi_register_lapic.

Signed-off-by: Petr Vandrovec <petr@vmware.com>
Signed-off-by: Alok N Kataria <akataria@vmware.com>
Cc : Toshi Kani <toshi.kani@hp.com>


Index: linux-2.6/arch/x86/kernel/acpi/boot.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/acpi/boot.c	2012-01-24 14:48:56.000000000 -0800
+++ linux-2.6/arch/x86/kernel/acpi/boot.c	2012-03-08 13:25:39.000000000 -0800
@@ -642,6 +642,7 @@ static int __cpuinit _acpi_map_lsapic(ac
 	kfree(buffer.pointer);
 	buffer.length = ACPI_ALLOCATE_BUFFER;
 	buffer.pointer = NULL;
+	lapic = NULL;
 
 	if (!alloc_cpumask_var(&tmp_map, GFP_KERNEL))
 		goto out;
@@ -650,7 +651,7 @@ static int __cpuinit _acpi_map_lsapic(ac
 		goto free_tmp_map;
 
 	cpumask_copy(tmp_map, cpu_present_mask);
-	acpi_register_lapic(physid, lapic->lapic_flags & ACPI_MADT_ENABLED);
+	acpi_register_lapic(physid, ACPI_MADT_ENABLED);
 
 	/*
 	 * If mp_register_lapic successfully generates a new logical cpu

Re: [PATCH 3.3.0-rc3] Fix use-after-free in acpi_map_lsapic

[Toshi Kani]

Hi Alok,

On Thu, 2012-03-08 at 13:33 -0800, Alok Kataria wrote:
> Hi Toshi, 
> 

> > 
> > The change looks good. I suggest you also add the following line to
> > prevent such bug in future.
> > 
> >         kfree(buffer.pointer);
> >         buffer.length = ACPI_ALLOCATE_BUFFER;
> >         buffer.pointer = NULL;
> > +       lapic = NULL;
> 
> That's a good suggestion, below is the updated patch. Thanks !!

Looks good. Thanks for the update.
-Toshi


> --
> 
> From: Petr Vandrovec <petr@vmware.com>
> 
> When processor is being hot-added to the system, acpi_map_lsapic invokes
> ACPI _MAT method to find APIC ID and flags, verifies that returned structure
> is indeed ACPI's local APIC structure, and that flags contain MADT_ENABLED
> bit.  Then saves APIC ID, frees structure - and accesses structure when
> computing arguments for acpi_register_lapic call.  Which sometime leads
> to acpi_register_lapic call being made with second argument zero, failing
> to bring processor online with error 'Unable to map lapic to logical cpu
> number'.
> 
> As lapic->lapic_flags & ACPI_MADT_ENABLED was already confirmed to be non-zero
> few lines above, we can just pass unconditional ACPI_MADT_ENABLED to the
> acpi_register_lapic.
> 
> Signed-off-by: Petr Vandrovec <petr@vmware.com>
> Signed-off-by: Alok N Kataria <akataria@vmware.com>
> Cc : Toshi Kani <toshi.kani@hp.com>
> 
> 
> Index: linux-2.6/arch/x86/kernel/acpi/boot.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/acpi/boot.c	2012-01-24 14:48:56.000000000 -0800
> +++ linux-2.6/arch/x86/kernel/acpi/boot.c	2012-03-08 13:25:39.000000000 -0800
> @@ -642,6 +642,7 @@ static int __cpuinit _acpi_map_lsapic(ac
>  	kfree(buffer.pointer);
>  	buffer.length = ACPI_ALLOCATE_BUFFER;
>  	buffer.pointer = NULL;
> +	lapic = NULL;
>  
>  	if (!alloc_cpumask_var(&tmp_map, GFP_KERNEL))
>  		goto out;
> @@ -650,7 +651,7 @@ static int __cpuinit _acpi_map_lsapic(ac
>  		goto free_tmp_map;
>  
>  	cpumask_copy(tmp_map, cpu_present_mask);
> -	acpi_register_lapic(physid, lapic->lapic_flags & ACPI_MADT_ENABLED);
> +	acpi_register_lapic(physid, ACPI_MADT_ENABLED);
>  
>  	/*
>  	 * If mp_register_lapic successfully generates a new logical cpu
> 
> 
> 
>