Fix use-after-free in acpi_map_lsapic

PATCH In review Petr Vandrovec 3 participants 5 messages Feb 16, 2012 – Mar 8, 2012

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x86 ACPI

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Petr Vandrovec

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2012-02-16 00:06 UTC #0 lore raw

PATCH 1/1 Fix use-after-free in acpi_map_lsapic

From: Petr Vandrovec <[email protected]>

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 <[email protected]>

Signed-off-by Alok Kataria <[email protected]>

arch/x86/kernel/acpi/boot.c +1 -1

index ce664f3..a4a0901 100644
@@ -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

Alok Kataria

2012-03-07 19:48 UTC #1 lore raw

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

Quoted 34 lines · Petr Vandrovec

From: Petr Vandrovec <[email protected]>
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 <[email protected]>
Signed-off-by Alok Kataria <[email protected]>
arch/x86/kernel/acpi/boot.c +1 -1
index ce664f3..a4a0901 100644
@@ -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

Toshi Kani

2012-03-08 21:01 UTC #2 lore raw

Quoted 38 lines · 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
Quoted 28 lines · Petr Vandrovec
From: Petr Vandrovec <[email protected]>
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 <[email protected]>
Signed-off-by Alok Kataria <[email protected]>
arch/x86/kernel/acpi/boot.c +0 -0
index ce664f3..a4a0901 100644
@@ -650,7 +650,7 @@ static int __cpuinit _acpi_map_lsapic(acpi_handle handle, int *pcpu)
 		goto free_tmp_map;
 

Quoted 3 lines

arch/x86/kernel/acpi/boot.c static int __cpuinit _acpi_map_lsapic(acpi_handle handle, int *pcpu) · line 653
Quoted 3 lines
arch/x86/kernel/acpi/boot.c +1 -1
 	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

Quoted 8 lines

arch/x86/kernel/acpi/boot.c static int __cpuinit _acpi_map_lsapic(acpi_handle handle, int *pcpu) · line 656
Quoted 3 lines
arch/x86/kernel/acpi/boot.c +0 -0
 	/*
 	 * If mp_register_lapic successfully generates a new logical cpu
--
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Alok Kataria

2012-03-08 21:33 UTC #3 lore raw

Hi Toshi,

Quoted 46 lines · Toshi Kani

Quoted 38 lines · 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
Quoted 28 lines · Petr Vandrovec
From: Petr Vandrovec <[email protected]>
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 <[email protected]>
Signed-off-by Alok Kataria <[email protected]>
arch/x86/kernel/acpi/boot.c +0 -0
index ce664f3..a4a0901 100644
@@ -650,7 +650,7 @@ static int __cpuinit _acpi_map_lsapic(acpi_handle handle, int *pcpu)
 		goto free_tmp_map;
 
Quoted 3 lines
arch/x86/kernel/acpi/boot.c static int __cpuinit _acpi_map_lsapic(acpi_handle handle, int *pcpu) · line 653
Quoted 3 lines
arch/x86/kernel/acpi/boot.c +1 -1
 	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.

Quoted 4 lines

        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 <[email protected]>

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 <[email protected]>

Signed-off-by Alok N Kataria <[email protected]>

Cc Toshi Kani <[email protected]>

arch/x86/kernel/acpi/boot.c +2 -1

Index: linux-2.6/arch/x86/kernel/acpi/boot.c
===================================================================
@@ -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

Toshi Kani

2012-03-08 22:34 UTC #4 lore raw

Hi Alok,

Quoted 7 lines · Alok Kataria

Hi Toshi,
Quoted 4 lines
The change looks good. I suggest you also add the following line to prevent such bug in future.

Quoted 6 lines

Quoted 4 lines
        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

Quoted 47 lines

--
From: Petr Vandrovec <[email protected]>
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 <[email protected]>
Signed-off-by Alok N Kataria <[email protected]>
Cc Toshi Kani <[email protected]>
Index: linux-2.6/arch/x86/kernel/acpi/boot.c
===================================================================
arch/x86/kernel/acpi/boot.c +2 -1
@@ -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