Patchwork [v11,5/5] x86/boot/KASLR: Walk srat tables to filter immovable memory

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Submitter Chao Fan
Date Nov. 12, 2018, 9:46 a.m.
Message ID <20181112094645.4879-6-fanc.fnst@cn.fujitsu.com>
Download mbox | patch
Permalink /patch/654529/
State New
Headers show

Comments

Chao Fan - Nov. 12, 2018, 9:46 a.m.
KASLR may randomly chooses some positions which are located in movable
memory regions. This will break memory hotplug feature and make the
movable memory chosen by KASLR can't be removed.

The solution is limite KASLR to choose memory regions in immovable
node according to SRAT tables.

If CONFIG_MEMORY_HOTREMOVE enabled, walk through the SRAT memory
tables and store those immovable memory regions so that KASLR can get
where to choose for randomization.

If the amount of immovable memory regions is not zero, which
means the immovable memory regions existing. Calculate the intersection
between memory regions from e820/efi memory table and immovable memory
regions.

Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
---
 arch/x86/boot/compressed/kaslr.c | 77 +++++++++++++++++++++++++++-----
 1 file changed, 66 insertions(+), 11 deletions(-)
Borislav Petkov - Nov. 16, 2018, 1:50 p.m.
Subject: Re: [PATCH v11 5/5] x86/boot/KASLR: Walk srat tables to filter immovable memory

s/srat/SRAT/g

On Mon, Nov 12, 2018 at 05:46:45PM +0800, Chao Fan wrote:
> KASLR may randomly chooses some positions which are located in movable

		    choose

> memory regions. This will break memory hotplug feature and make the
> movable memory chosen by KASLR can't be removed.

			by KASLR practically immovable.

:)

> The solution is limite KASLR to choose memory regions in immovable

limite?

"to limit"

> node according to SRAT tables.
> 
> If CONFIG_MEMORY_HOTREMOVE enabled, walk through the SRAT memory

			   *is* enabled,

> tables and store those immovable memory regions so that KASLR can get
> where to choose for randomization.
> 
> If the amount of immovable memory regions is not zero, which
> means the immovable memory regions existing. Calculate the intersection
> between memory regions from e820/efi memory table and immovable memory
> regions.

This is explaining *what* the patch does and generally doesn't need to
be in the commit messge as people can read it in the patch itself.

> Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
> ---
>  arch/x86/boot/compressed/kaslr.c | 77 +++++++++++++++++++++++++++-----
>  1 file changed, 66 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index b251572e77af..174d2114045e 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -97,6 +97,11 @@ static bool memmap_too_large;
>  /* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
>  static unsigned long long mem_limit = ULLONG_MAX;
>  
> +#ifdef CONFIG_MEMORY_HOTREMOVE
> +/* Store the immovable memory regions */
> +extern struct mem_vector immovable_mem[MAX_NUMNODES*2];
> +#endif

For this and the other occurrences of ifdef CONFIG_MEMORY_HOTREMOVE,
define empty stubs for those functions in a header and remove the
ifdeffery at the call sites.

> +
>  
>  enum mem_avoid_index {
>  	MEM_AVOID_ZO_RANGE = 0,
> @@ -413,6 +418,11 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
>  	/* Mark the memmap regions we need to avoid */
>  	handle_mem_options();
>  
> +#ifdef CONFIG_MEMORY_HOTREMOVE
> +	/* Mark the immovable regions we need to choose */
> +	get_immovable_mem();
> +#endif
> +
>  #ifdef CONFIG_X86_VERBOSE_BOOTUP
>  	/* Make sure video RAM can be used. */
>  	add_identity_map(0, PMD_SIZE);
> @@ -568,9 +578,9 @@ static unsigned long slots_fetch_random(void)
>  	return 0;
>  }
>  
> -static void process_mem_region(struct mem_vector *entry,
> -			       unsigned long minimum,
> -			       unsigned long image_size)
> +static void slots_count(struct mem_vector *entry,

That's a strange rename.

__process_mem_region() makes more sense to me.

> +			unsigned long minimum,
> +			unsigned long image_size)
>  {
>  	struct mem_vector region, overlap;
>  	unsigned long start_orig, end;
> @@ -646,6 +656,57 @@ static void process_mem_region(struct mem_vector *entry,
>  	}
>  }
>  
> +static bool process_mem_region(struct mem_vector *region,
> +			       unsigned long long minimum,
> +			       unsigned long long image_size)
> +{
> +	int i;
> +	/*
> +	 * If no immovable memory found, or MEMORY_HOTREMOVE disabled,
> +	 * walk all the regions, so use region directely.

"directly"

> +	 */
> +	if (num_immovable_mem == 0) {

	if (!...

> +		slots_count(region, minimum, image_size);
> +
> +		if (slot_area_index == MAX_SLOT_AREA) {
> +			debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n");
> +			return 1;
> +		}
> +		return 0;
> +	}
> +
Chao Fan - Nov. 19, 2018, 1:31 a.m.
On Fri, Nov 16, 2018 at 02:50:39PM +0100, Borislav Petkov wrote:
> Subject: Re: [PATCH v11 5/5] x86/boot/KASLR: Walk srat tables to filter immovable memory
>
>s/srat/SRAT/g
>
>On Mon, Nov 12, 2018 at 05:46:45PM +0800, Chao Fan wrote:
>> KASLR may randomly chooses some positions which are located in movable
>
>		    choose
>
>> memory regions. This will break memory hotplug feature and make the
>> movable memory chosen by KASLR can't be removed.
>
>			by KASLR practically immovable.

Thanks,

>
>:)
>
>> The solution is limite KASLR to choose memory regions in immovable
>
>limite?
>
>"to limit"
>
>> node according to SRAT tables.
>> 
>> If CONFIG_MEMORY_HOTREMOVE enabled, walk through the SRAT memory
>
>			   *is* enabled,
>
>> tables and store those immovable memory regions so that KASLR can get
>> where to choose for randomization.
>> 
>> If the amount of immovable memory regions is not zero, which
>> means the immovable memory regions existing. Calculate the intersection
>> between memory regions from e820/efi memory table and immovable memory
>> regions.
>
>This is explaining *what* the patch does and generally doesn't need to
>be in the commit messge as people can read it in the patch itself.

OK,

>
>> Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
>> ---
>>  arch/x86/boot/compressed/kaslr.c | 77 +++++++++++++++++++++++++++-----
>>  1 file changed, 66 insertions(+), 11 deletions(-)
>> 
>> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
>> index b251572e77af..174d2114045e 100644
>> --- a/arch/x86/boot/compressed/kaslr.c
>> +++ b/arch/x86/boot/compressed/kaslr.c
>> @@ -97,6 +97,11 @@ static bool memmap_too_large;
>>  /* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
>>  static unsigned long long mem_limit = ULLONG_MAX;
>>  
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +/* Store the immovable memory regions */
>> +extern struct mem_vector immovable_mem[MAX_NUMNODES*2];
>> +#endif
>
>For this and the other occurrences of ifdef CONFIG_MEMORY_HOTREMOVE,
>define empty stubs for those functions in a header and remove the
>ifdeffery at the call sites.

OK,

>
>> +
>>  
>>  enum mem_avoid_index {
>>  	MEM_AVOID_ZO_RANGE = 0,
>> @@ -413,6 +418,11 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
>>  	/* Mark the memmap regions we need to avoid */
>>  	handle_mem_options();
>>  
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +	/* Mark the immovable regions we need to choose */
>> +	get_immovable_mem();
>> +#endif
>> +
>>  #ifdef CONFIG_X86_VERBOSE_BOOTUP
>>  	/* Make sure video RAM can be used. */
>>  	add_identity_map(0, PMD_SIZE);
>> @@ -568,9 +578,9 @@ static unsigned long slots_fetch_random(void)
>>  	return 0;
>>  }
>>  
>> -static void process_mem_region(struct mem_vector *entry,
>> -			       unsigned long minimum,
>> -			       unsigned long image_size)
>> +static void slots_count(struct mem_vector *entry,
>
>That's a strange rename.
>
I will change it.

Thanks,
Chao Fan

>__process_mem_region() makes more sense to me.
>
>> +			unsigned long minimum,
>> +			unsigned long image_size)
>>  {
>>  	struct mem_vector region, overlap;
>>  	unsigned long start_orig, end;
>> @@ -646,6 +656,57 @@ static void process_mem_region(struct mem_vector *entry,
>>  	}
>>  }
>>  
>> +static bool process_mem_region(struct mem_vector *region,
>> +			       unsigned long long minimum,
>> +			       unsigned long long image_size)
>> +{
>> +	int i;
>> +	/*
>> +	 * If no immovable memory found, or MEMORY_HOTREMOVE disabled,
>> +	 * walk all the regions, so use region directely.
>
>"directly"
>
>> +	 */
>> +	if (num_immovable_mem == 0) {
>
>	if (!...
>
>> +		slots_count(region, minimum, image_size);
>> +
>> +		if (slot_area_index == MAX_SLOT_AREA) {
>> +			debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n");
>> +			return 1;
>> +		}
>> +		return 0;
>> +	}
>> +
>
>-- 
>Regards/Gruss,
>    Boris.
>
>Good mailing practices for 400: avoid top-posting and trim the reply.
>
>

Patch

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index b251572e77af..174d2114045e 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -97,6 +97,11 @@  static bool memmap_too_large;
 /* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
 static unsigned long long mem_limit = ULLONG_MAX;
 
+#ifdef CONFIG_MEMORY_HOTREMOVE
+/* Store the immovable memory regions */
+extern struct mem_vector immovable_mem[MAX_NUMNODES*2];
+#endif
+
 
 enum mem_avoid_index {
 	MEM_AVOID_ZO_RANGE = 0,
@@ -413,6 +418,11 @@  static void mem_avoid_init(unsigned long input, unsigned long input_size,
 	/* Mark the memmap regions we need to avoid */
 	handle_mem_options();
 
+#ifdef CONFIG_MEMORY_HOTREMOVE
+	/* Mark the immovable regions we need to choose */
+	get_immovable_mem();
+#endif
+
 #ifdef CONFIG_X86_VERBOSE_BOOTUP
 	/* Make sure video RAM can be used. */
 	add_identity_map(0, PMD_SIZE);
@@ -568,9 +578,9 @@  static unsigned long slots_fetch_random(void)
 	return 0;
 }
 
-static void process_mem_region(struct mem_vector *entry,
-			       unsigned long minimum,
-			       unsigned long image_size)
+static void slots_count(struct mem_vector *entry,
+			unsigned long minimum,
+			unsigned long image_size)
 {
 	struct mem_vector region, overlap;
 	unsigned long start_orig, end;
@@ -646,6 +656,57 @@  static void process_mem_region(struct mem_vector *entry,
 	}
 }
 
+static bool process_mem_region(struct mem_vector *region,
+			       unsigned long long minimum,
+			       unsigned long long image_size)
+{
+	int i;
+	/*
+	 * If no immovable memory found, or MEMORY_HOTREMOVE disabled,
+	 * walk all the regions, so use region directely.
+	 */
+	if (num_immovable_mem == 0) {
+		slots_count(region, minimum, image_size);
+
+		if (slot_area_index == MAX_SLOT_AREA) {
+			debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n");
+			return 1;
+		}
+		return 0;
+	}
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+	/*
+	 * If immovable memory found, filter the intersection between
+	 * immovable memory and region to slots_count.
+	 * Otherwise, go on old code.
+	 */
+	for (i = 0; i < num_immovable_mem; i++) {
+		struct mem_vector entry;
+		unsigned long long start, end, entry_end, region_end;
+
+		if (!mem_overlaps(region, &immovable_mem[i]))
+			continue;
+
+		start = immovable_mem[i].start;
+		end = start + immovable_mem[i].size;
+		region_end = region->start + region->size;
+
+		entry.start = clamp(region->start, start, end);
+		entry_end = clamp(region_end, start, end);
+		entry.size = entry_end - entry.start;
+
+		slots_count(&entry, minimum, image_size);
+
+		if (slot_area_index == MAX_SLOT_AREA) {
+			debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n");
+			return 1;
+		}
+	}
+	return 0;
+#endif
+}
+
 #ifdef CONFIG_EFI
 /*
  * Returns true if mirror region found (and must have been processed
@@ -711,11 +772,8 @@  process_efi_entries(unsigned long minimum, unsigned long image_size)
 
 		region.start = md->phys_addr;
 		region.size = md->num_pages << EFI_PAGE_SHIFT;
-		process_mem_region(&region, minimum, image_size);
-		if (slot_area_index == MAX_SLOT_AREA) {
-			debug_putstr("Aborted EFI scan (slot_areas full)!\n");
+		if (process_mem_region(&region, minimum, image_size))
 			break;
-		}
 	}
 	return true;
 }
@@ -742,11 +800,8 @@  static void process_e820_entries(unsigned long minimum,
 			continue;
 		region.start = entry->addr;
 		region.size = entry->size;
-		process_mem_region(&region, minimum, image_size);
-		if (slot_area_index == MAX_SLOT_AREA) {
-			debug_putstr("Aborted e820 scan (slot_areas full)!\n");
+		if (process_mem_region(&region, minimum, image_size))
 			break;
-		}
 	}
 }