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SubjectRe: [PATCH] x86/boot/KASLR: Extend movable_node option for KASLR
On Thu, Aug 3, 2017 at 5:17 AM, Dou Liyang <douly.fnst@cn.fujitsu.com> wrote:
> movable_node is a boot-time switch to make hot-pluggable memory
> NUMA nodes to be movable. This option is based on an assumption
> that any node which the kernel resides in is defined as
> un-hotpluggable. Linux can allocates memory near the kernel image
> to try the best to keep the kernel away from hotpluggable memory
> in the same NUMA node. So other nodes can be movable.
>
> But, KASLR doesn't know which node is un-hotpluggable, the all
> hotpluggable memory ranges is recorded in ACPI SRAT table, SRAT
> is not parsed. So, KASLR may randomize the kernel in a movable
> node which will be immovable.
>
> Extend movable_node option to restrict kernel to be randomized in
> immovable nodes by adding a parameter. this parameter sets up
> the boundaries between the movable nodes and immovable nodes.
>
> Reported-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
> Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>

This seems reasonable to me. Thanks for the fix!

Reviewed-by: Kees Cook <keescook@chromium.org>

> ---
> Documentation/admin-guide/kernel-parameters.txt | 11 +++++++++--
> arch/x86/boot/compressed/kaslr.c | 19 ++++++++++++++++---
> 2 files changed, 25 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index d9c171c..44c7e33 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2305,7 +2305,8 @@
> mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
> reporting absolute coordinates, such as tablets
>
> - movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
> + movablecore=nn[KMG]
> + [KNL,X86,IA-64,PPC] This parameter
> is similar to kernelcore except it specifies the
> amount of memory used for migratable allocations.
> If both kernelcore and movablecore is specified,
> @@ -2315,12 +2316,18 @@
> that the amount of memory usable for all allocations
> is not too small.
>
> - movable_node [KNL] Boot-time switch to make hotplugable memory
> + movable_node [KNL] Boot-time switch to make hot-pluggable memory
> NUMA nodes to be movable. This means that the memory
> of such nodes will be usable only for movable
> allocations which rules out almost all kernel
> allocations. Use with caution!
>
> + movable_node=nn[KMG]
> + [KNL] Extend movable_node to work well with KASLR. This
> + parameter is the boundaries between the movable nodes
> + and immovable nodes, the memory which exceeds it will
> + be regarded as hot-pluggable.
> +
> MTD_Partition= [MTD]
> Format: <name>,<region-number>,<size>,<offset>
>
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index 91f27ab..7e2351b 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -89,7 +89,10 @@ struct mem_vector {
> static bool memmap_too_large;
>
>
> -/* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
> +/*
> + * Store memory limit specified by the following situations:
> + * "mem=nn[KMG]" or "memmap=nn[KMG]" or "movable_node=nn[KMG]"
> + */
> unsigned long long mem_limit = ULLONG_MAX;
>
>
> @@ -212,7 +215,8 @@ static int handle_mem_memmap(void)
> char *param, *val;
> u64 mem_size;
>
> - if (!strstr(args, "memmap=") && !strstr(args, "mem="))
> + if (!strstr(args, "memmap=") && !strstr(args, "mem=") &&
> + !strstr(args, "movable_node="))
> return 0;
>
> tmp_cmdline = malloc(len + 1);
> @@ -247,7 +251,16 @@ static int handle_mem_memmap(void)
> free(tmp_cmdline);
> return -EINVAL;
> }
> - mem_limit = mem_size;
> + mem_limit = mem_limit > mem_size ? mem_size : mem_limit;
> + } else if (!strcmp(param, "movable_node")) {
> + char *p = val;
> +
> + mem_size = memparse(p, &p);
> + if (mem_size == 0) {
> + free(tmp_cmdline);
> + return -EINVAL;
> + }
> + mem_limit = mem_limit > mem_size ? mem_size : mem_limit;
> }
> }
>
> --
> 2.5.5
>
>
>



--
Kees Cook
Pixel Security

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