* [PATCH] linux: Do not allow slab caches to be merged
@ 2022-08-01 17:39 Peter Müller
2022-08-01 20:19 ` Michael Tremer
2022-08-06 8:00 ` Peter Müller
0 siblings, 2 replies; 6+ messages in thread
From: Peter Müller @ 2022-08-01 17:39 UTC (permalink / raw)
To: development
[-- Attachment #1: Type: text/plain, Size: 3021 bytes --]
>From the kernel documentation:
> For reduced kernel memory fragmentation, slab caches can be
> merged when they share the same size and other characteristics.
> This carries a risk of kernel heap overflows being able to
> overwrite objects from merged caches (and more easily control
> cache layout), which makes such heap attacks easier to exploit
> by attackers. By keeping caches unmerged, these kinds of exploits
> can usually only damage objects in the same cache. [...]
Thus, it is more sane to leave slab merging disabled. KSPP and ClipOS
recommend this as well.
Signed-off-by: Peter Müller <peter.mueller(a)ipfire.org>
---
config/kernel/kernel.config.aarch64-ipfire | 2 +-
config/kernel/kernel.config.armv6l-ipfire | 2 +-
config/kernel/kernel.config.riscv64-ipfire | 2 +-
config/kernel/kernel.config.x86_64-ipfire | 2 +-
4 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/config/kernel/kernel.config.aarch64-ipfire b/config/kernel/kernel.config.aarch64-ipfire
index 9232335ff..023c3d5aa 100644
--- a/config/kernel/kernel.config.aarch64-ipfire
+++ b/config/kernel/kernel.config.aarch64-ipfire
@@ -247,7 +247,7 @@ CONFIG_VM_EVENT_COUNTERS=y
# CONFIG_SLAB is not set
CONFIG_SLUB=y
# CONFIG_SLOB is not set
-CONFIG_SLAB_MERGE_DEFAULT=y
+# CONFIG_SLAB_MERGE_DEFAULT is not set
CONFIG_SLAB_FREELIST_RANDOM=y
CONFIG_SLAB_FREELIST_HARDENED=y
CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
diff --git a/config/kernel/kernel.config.armv6l-ipfire b/config/kernel/kernel.config.armv6l-ipfire
index dc0aee51b..b4587826e 100644
--- a/config/kernel/kernel.config.armv6l-ipfire
+++ b/config/kernel/kernel.config.armv6l-ipfire
@@ -250,7 +250,7 @@ CONFIG_VM_EVENT_COUNTERS=y
# CONFIG_SLAB is not set
CONFIG_SLUB=y
# CONFIG_SLOB is not set
-CONFIG_SLAB_MERGE_DEFAULT=y
+# CONFIG_SLAB_MERGE_DEFAULT is not set
CONFIG_SLAB_FREELIST_RANDOM=y
CONFIG_SLAB_FREELIST_HARDENED=y
CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
diff --git a/config/kernel/kernel.config.riscv64-ipfire b/config/kernel/kernel.config.riscv64-ipfire
index 0801f4389..fb7cda4dd 100644
--- a/config/kernel/kernel.config.riscv64-ipfire
+++ b/config/kernel/kernel.config.riscv64-ipfire
@@ -230,7 +230,7 @@ CONFIG_VM_EVENT_COUNTERS=y
# CONFIG_SLAB is not set
CONFIG_SLUB=y
# CONFIG_SLOB is not set
-CONFIG_SLAB_MERGE_DEFAULT=y
+# CONFIG_SLAB_MERGE_DEFAULT is not set
CONFIG_SLAB_FREELIST_RANDOM=y
CONFIG_SLAB_FREELIST_HARDENED=y
CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
diff --git a/config/kernel/kernel.config.x86_64-ipfire b/config/kernel/kernel.config.x86_64-ipfire
index 40975b5fc..d3792cbb7 100644
--- a/config/kernel/kernel.config.x86_64-ipfire
+++ b/config/kernel/kernel.config.x86_64-ipfire
@@ -270,7 +270,7 @@ CONFIG_VM_EVENT_COUNTERS=y
# CONFIG_SLAB is not set
CONFIG_SLUB=y
# CONFIG_SLOB is not set
-CONFIG_SLAB_MERGE_DEFAULT=y
+# CONFIG_SLAB_MERGE_DEFAULT is not set
CONFIG_SLAB_FREELIST_RANDOM=y
CONFIG_SLAB_FREELIST_HARDENED=y
CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
--
2.35.3
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] linux: Do not allow slab caches to be merged
2022-08-01 17:39 [PATCH] linux: Do not allow slab caches to be merged Peter Müller
@ 2022-08-01 20:19 ` Michael Tremer
2022-08-02 9:50 ` Peter Müller
2022-08-06 8:00 ` Peter Müller
1 sibling, 1 reply; 6+ messages in thread
From: Michael Tremer @ 2022-08-01 20:19 UTC (permalink / raw)
To: development
[-- Attachment #1: Type: text/plain, Size: 3268 bytes --]
And there are no downsides to this whatsoever?
> On 1 Aug 2022, at 18:39, Peter Müller <peter.mueller(a)ipfire.org> wrote:
>
> From the kernel documentation:
>
>> For reduced kernel memory fragmentation, slab caches can be
>> merged when they share the same size and other characteristics.
>> This carries a risk of kernel heap overflows being able to
>> overwrite objects from merged caches (and more easily control
>> cache layout), which makes such heap attacks easier to exploit
>> by attackers. By keeping caches unmerged, these kinds of exploits
>> can usually only damage objects in the same cache. [...]
>
> Thus, it is more sane to leave slab merging disabled. KSPP and ClipOS
> recommend this as well.
>
> Signed-off-by: Peter Müller <peter.mueller(a)ipfire.org>
> ---
> config/kernel/kernel.config.aarch64-ipfire | 2 +-
> config/kernel/kernel.config.armv6l-ipfire | 2 +-
> config/kernel/kernel.config.riscv64-ipfire | 2 +-
> config/kernel/kernel.config.x86_64-ipfire | 2 +-
> 4 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/config/kernel/kernel.config.aarch64-ipfire b/config/kernel/kernel.config.aarch64-ipfire
> index 9232335ff..023c3d5aa 100644
> --- a/config/kernel/kernel.config.aarch64-ipfire
> +++ b/config/kernel/kernel.config.aarch64-ipfire
> @@ -247,7 +247,7 @@ CONFIG_VM_EVENT_COUNTERS=y
> # CONFIG_SLAB is not set
> CONFIG_SLUB=y
> # CONFIG_SLOB is not set
> -CONFIG_SLAB_MERGE_DEFAULT=y
> +# CONFIG_SLAB_MERGE_DEFAULT is not set
> CONFIG_SLAB_FREELIST_RANDOM=y
> CONFIG_SLAB_FREELIST_HARDENED=y
> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
> diff --git a/config/kernel/kernel.config.armv6l-ipfire b/config/kernel/kernel.config.armv6l-ipfire
> index dc0aee51b..b4587826e 100644
> --- a/config/kernel/kernel.config.armv6l-ipfire
> +++ b/config/kernel/kernel.config.armv6l-ipfire
> @@ -250,7 +250,7 @@ CONFIG_VM_EVENT_COUNTERS=y
> # CONFIG_SLAB is not set
> CONFIG_SLUB=y
> # CONFIG_SLOB is not set
> -CONFIG_SLAB_MERGE_DEFAULT=y
> +# CONFIG_SLAB_MERGE_DEFAULT is not set
> CONFIG_SLAB_FREELIST_RANDOM=y
> CONFIG_SLAB_FREELIST_HARDENED=y
> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
> diff --git a/config/kernel/kernel.config.riscv64-ipfire b/config/kernel/kernel.config.riscv64-ipfire
> index 0801f4389..fb7cda4dd 100644
> --- a/config/kernel/kernel.config.riscv64-ipfire
> +++ b/config/kernel/kernel.config.riscv64-ipfire
> @@ -230,7 +230,7 @@ CONFIG_VM_EVENT_COUNTERS=y
> # CONFIG_SLAB is not set
> CONFIG_SLUB=y
> # CONFIG_SLOB is not set
> -CONFIG_SLAB_MERGE_DEFAULT=y
> +# CONFIG_SLAB_MERGE_DEFAULT is not set
> CONFIG_SLAB_FREELIST_RANDOM=y
> CONFIG_SLAB_FREELIST_HARDENED=y
> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
> diff --git a/config/kernel/kernel.config.x86_64-ipfire b/config/kernel/kernel.config.x86_64-ipfire
> index 40975b5fc..d3792cbb7 100644
> --- a/config/kernel/kernel.config.x86_64-ipfire
> +++ b/config/kernel/kernel.config.x86_64-ipfire
> @@ -270,7 +270,7 @@ CONFIG_VM_EVENT_COUNTERS=y
> # CONFIG_SLAB is not set
> CONFIG_SLUB=y
> # CONFIG_SLOB is not set
> -CONFIG_SLAB_MERGE_DEFAULT=y
> +# CONFIG_SLAB_MERGE_DEFAULT is not set
> CONFIG_SLAB_FREELIST_RANDOM=y
> CONFIG_SLAB_FREELIST_HARDENED=y
> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
> --
> 2.35.3
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] linux: Do not allow slab caches to be merged
2022-08-01 20:19 ` Michael Tremer
@ 2022-08-02 9:50 ` Peter Müller
0 siblings, 0 replies; 6+ messages in thread
From: Peter Müller @ 2022-08-02 9:50 UTC (permalink / raw)
To: development
[-- Attachment #1: Type: text/plain, Size: 3483 bytes --]
Hello Michael,
aside from increased kernel memory fragmentation, none I am aware of.
Thanks, and best regards,
Peter Müller
> And there are no downsides to this whatsoever?
>
>> On 1 Aug 2022, at 18:39, Peter Müller <peter.mueller(a)ipfire.org> wrote:
>>
>> From the kernel documentation:
>>
>>> For reduced kernel memory fragmentation, slab caches can be
>>> merged when they share the same size and other characteristics.
>>> This carries a risk of kernel heap overflows being able to
>>> overwrite objects from merged caches (and more easily control
>>> cache layout), which makes such heap attacks easier to exploit
>>> by attackers. By keeping caches unmerged, these kinds of exploits
>>> can usually only damage objects in the same cache. [...]
>>
>> Thus, it is more sane to leave slab merging disabled. KSPP and ClipOS
>> recommend this as well.
>>
>> Signed-off-by: Peter Müller <peter.mueller(a)ipfire.org>
>> ---
>> config/kernel/kernel.config.aarch64-ipfire | 2 +-
>> config/kernel/kernel.config.armv6l-ipfire | 2 +-
>> config/kernel/kernel.config.riscv64-ipfire | 2 +-
>> config/kernel/kernel.config.x86_64-ipfire | 2 +-
>> 4 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/config/kernel/kernel.config.aarch64-ipfire b/config/kernel/kernel.config.aarch64-ipfire
>> index 9232335ff..023c3d5aa 100644
>> --- a/config/kernel/kernel.config.aarch64-ipfire
>> +++ b/config/kernel/kernel.config.aarch64-ipfire
>> @@ -247,7 +247,7 @@ CONFIG_VM_EVENT_COUNTERS=y
>> # CONFIG_SLAB is not set
>> CONFIG_SLUB=y
>> # CONFIG_SLOB is not set
>> -CONFIG_SLAB_MERGE_DEFAULT=y
>> +# CONFIG_SLAB_MERGE_DEFAULT is not set
>> CONFIG_SLAB_FREELIST_RANDOM=y
>> CONFIG_SLAB_FREELIST_HARDENED=y
>> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
>> diff --git a/config/kernel/kernel.config.armv6l-ipfire b/config/kernel/kernel.config.armv6l-ipfire
>> index dc0aee51b..b4587826e 100644
>> --- a/config/kernel/kernel.config.armv6l-ipfire
>> +++ b/config/kernel/kernel.config.armv6l-ipfire
>> @@ -250,7 +250,7 @@ CONFIG_VM_EVENT_COUNTERS=y
>> # CONFIG_SLAB is not set
>> CONFIG_SLUB=y
>> # CONFIG_SLOB is not set
>> -CONFIG_SLAB_MERGE_DEFAULT=y
>> +# CONFIG_SLAB_MERGE_DEFAULT is not set
>> CONFIG_SLAB_FREELIST_RANDOM=y
>> CONFIG_SLAB_FREELIST_HARDENED=y
>> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
>> diff --git a/config/kernel/kernel.config.riscv64-ipfire b/config/kernel/kernel.config.riscv64-ipfire
>> index 0801f4389..fb7cda4dd 100644
>> --- a/config/kernel/kernel.config.riscv64-ipfire
>> +++ b/config/kernel/kernel.config.riscv64-ipfire
>> @@ -230,7 +230,7 @@ CONFIG_VM_EVENT_COUNTERS=y
>> # CONFIG_SLAB is not set
>> CONFIG_SLUB=y
>> # CONFIG_SLOB is not set
>> -CONFIG_SLAB_MERGE_DEFAULT=y
>> +# CONFIG_SLAB_MERGE_DEFAULT is not set
>> CONFIG_SLAB_FREELIST_RANDOM=y
>> CONFIG_SLAB_FREELIST_HARDENED=y
>> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
>> diff --git a/config/kernel/kernel.config.x86_64-ipfire b/config/kernel/kernel.config.x86_64-ipfire
>> index 40975b5fc..d3792cbb7 100644
>> --- a/config/kernel/kernel.config.x86_64-ipfire
>> +++ b/config/kernel/kernel.config.x86_64-ipfire
>> @@ -270,7 +270,7 @@ CONFIG_VM_EVENT_COUNTERS=y
>> # CONFIG_SLAB is not set
>> CONFIG_SLUB=y
>> # CONFIG_SLOB is not set
>> -CONFIG_SLAB_MERGE_DEFAULT=y
>> +# CONFIG_SLAB_MERGE_DEFAULT is not set
>> CONFIG_SLAB_FREELIST_RANDOM=y
>> CONFIG_SLAB_FREELIST_HARDENED=y
>> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
>> --
>> 2.35.3
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] linux: Do not allow slab caches to be merged
2022-08-01 17:39 [PATCH] linux: Do not allow slab caches to be merged Peter Müller
2022-08-01 20:19 ` Michael Tremer
@ 2022-08-06 8:00 ` Peter Müller
2022-08-06 11:41 ` Paul Simmons
2022-08-06 12:05 ` Michael Tremer
1 sibling, 2 replies; 6+ messages in thread
From: Peter Müller @ 2022-08-06 8:00 UTC (permalink / raw)
To: development
[-- Attachment #1: Type: text/plain, Size: 3244 bytes --]
Hello *,
any vetoes / endorsements of this? :-)
Thanks, and best regards,
Peter Müller
> From the kernel documentation:
>
>> For reduced kernel memory fragmentation, slab caches can be
>> merged when they share the same size and other characteristics.
>> This carries a risk of kernel heap overflows being able to
>> overwrite objects from merged caches (and more easily control
>> cache layout), which makes such heap attacks easier to exploit
>> by attackers. By keeping caches unmerged, these kinds of exploits
>> can usually only damage objects in the same cache. [...]
>
> Thus, it is more sane to leave slab merging disabled. KSPP and ClipOS
> recommend this as well.
>
> Signed-off-by: Peter Müller <peter.mueller(a)ipfire.org>
> ---
> config/kernel/kernel.config.aarch64-ipfire | 2 +-
> config/kernel/kernel.config.armv6l-ipfire | 2 +-
> config/kernel/kernel.config.riscv64-ipfire | 2 +-
> config/kernel/kernel.config.x86_64-ipfire | 2 +-
> 4 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/config/kernel/kernel.config.aarch64-ipfire b/config/kernel/kernel.config.aarch64-ipfire
> index 9232335ff..023c3d5aa 100644
> --- a/config/kernel/kernel.config.aarch64-ipfire
> +++ b/config/kernel/kernel.config.aarch64-ipfire
> @@ -247,7 +247,7 @@ CONFIG_VM_EVENT_COUNTERS=y
> # CONFIG_SLAB is not set
> CONFIG_SLUB=y
> # CONFIG_SLOB is not set
> -CONFIG_SLAB_MERGE_DEFAULT=y
> +# CONFIG_SLAB_MERGE_DEFAULT is not set
> CONFIG_SLAB_FREELIST_RANDOM=y
> CONFIG_SLAB_FREELIST_HARDENED=y
> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
> diff --git a/config/kernel/kernel.config.armv6l-ipfire b/config/kernel/kernel.config.armv6l-ipfire
> index dc0aee51b..b4587826e 100644
> --- a/config/kernel/kernel.config.armv6l-ipfire
> +++ b/config/kernel/kernel.config.armv6l-ipfire
> @@ -250,7 +250,7 @@ CONFIG_VM_EVENT_COUNTERS=y
> # CONFIG_SLAB is not set
> CONFIG_SLUB=y
> # CONFIG_SLOB is not set
> -CONFIG_SLAB_MERGE_DEFAULT=y
> +# CONFIG_SLAB_MERGE_DEFAULT is not set
> CONFIG_SLAB_FREELIST_RANDOM=y
> CONFIG_SLAB_FREELIST_HARDENED=y
> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
> diff --git a/config/kernel/kernel.config.riscv64-ipfire b/config/kernel/kernel.config.riscv64-ipfire
> index 0801f4389..fb7cda4dd 100644
> --- a/config/kernel/kernel.config.riscv64-ipfire
> +++ b/config/kernel/kernel.config.riscv64-ipfire
> @@ -230,7 +230,7 @@ CONFIG_VM_EVENT_COUNTERS=y
> # CONFIG_SLAB is not set
> CONFIG_SLUB=y
> # CONFIG_SLOB is not set
> -CONFIG_SLAB_MERGE_DEFAULT=y
> +# CONFIG_SLAB_MERGE_DEFAULT is not set
> CONFIG_SLAB_FREELIST_RANDOM=y
> CONFIG_SLAB_FREELIST_HARDENED=y
> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
> diff --git a/config/kernel/kernel.config.x86_64-ipfire b/config/kernel/kernel.config.x86_64-ipfire
> index 40975b5fc..d3792cbb7 100644
> --- a/config/kernel/kernel.config.x86_64-ipfire
> +++ b/config/kernel/kernel.config.x86_64-ipfire
> @@ -270,7 +270,7 @@ CONFIG_VM_EVENT_COUNTERS=y
> # CONFIG_SLAB is not set
> CONFIG_SLUB=y
> # CONFIG_SLOB is not set
> -CONFIG_SLAB_MERGE_DEFAULT=y
> +# CONFIG_SLAB_MERGE_DEFAULT is not set
> CONFIG_SLAB_FREELIST_RANDOM=y
> CONFIG_SLAB_FREELIST_HARDENED=y
> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] linux: Do not allow slab caches to be merged
2022-08-06 8:00 ` Peter Müller
@ 2022-08-06 11:41 ` Paul Simmons
2022-08-06 12:05 ` Michael Tremer
1 sibling, 0 replies; 6+ messages in thread
From: Paul Simmons @ 2022-08-06 11:41 UTC (permalink / raw)
To: development
[-- Attachment #1: Type: text/plain, Size: 3482 bytes --]
On 8/6/22 03:00, Peter Müller wrote:
> Hello *,
>
> any vetoes / endorsements of this? :-)
>
> Thanks, and best regards,
> Peter Müller
>
>> From the kernel documentation:
>>
>>> For reduced kernel memory fragmentation, slab caches can be
>>> merged when they share the same size and other characteristics.
>>> This carries a risk of kernel heap overflows being able to
>>> overwrite objects from merged caches (and more easily control
>>> cache layout), which makes such heap attacks easier to exploit
>>> by attackers. By keeping caches unmerged, these kinds of exploits
>>> can usually only damage objects in the same cache. [...]
>> Thus, it is more sane to leave slab merging disabled. KSPP and ClipOS
>> recommend this as well.
>>
>> Signed-off-by: Peter Müller <peter.mueller(a)ipfire.org>
>> ---
>> config/kernel/kernel.config.aarch64-ipfire | 2 +-
>> config/kernel/kernel.config.armv6l-ipfire | 2 +-
>> config/kernel/kernel.config.riscv64-ipfire | 2 +-
>> config/kernel/kernel.config.x86_64-ipfire | 2 +-
>> 4 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/config/kernel/kernel.config.aarch64-ipfire b/config/kernel/kernel.config.aarch64-ipfire
>> index 9232335ff..023c3d5aa 100644
>> --- a/config/kernel/kernel.config.aarch64-ipfire
>> +++ b/config/kernel/kernel.config.aarch64-ipfire
>> @@ -247,7 +247,7 @@ CONFIG_VM_EVENT_COUNTERS=y
>> # CONFIG_SLAB is not set
>> CONFIG_SLUB=y
>> # CONFIG_SLOB is not set
>> -CONFIG_SLAB_MERGE_DEFAULT=y
>> +# CONFIG_SLAB_MERGE_DEFAULT is not set
>> CONFIG_SLAB_FREELIST_RANDOM=y
>> CONFIG_SLAB_FREELIST_HARDENED=y
>> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
>> diff --git a/config/kernel/kernel.config.armv6l-ipfire b/config/kernel/kernel.config.armv6l-ipfire
>> index dc0aee51b..b4587826e 100644
>> --- a/config/kernel/kernel.config.armv6l-ipfire
>> +++ b/config/kernel/kernel.config.armv6l-ipfire
>> @@ -250,7 +250,7 @@ CONFIG_VM_EVENT_COUNTERS=y
>> # CONFIG_SLAB is not set
>> CONFIG_SLUB=y
>> # CONFIG_SLOB is not set
>> -CONFIG_SLAB_MERGE_DEFAULT=y
>> +# CONFIG_SLAB_MERGE_DEFAULT is not set
>> CONFIG_SLAB_FREELIST_RANDOM=y
>> CONFIG_SLAB_FREELIST_HARDENED=y
>> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
>> diff --git a/config/kernel/kernel.config.riscv64-ipfire b/config/kernel/kernel.config.riscv64-ipfire
>> index 0801f4389..fb7cda4dd 100644
>> --- a/config/kernel/kernel.config.riscv64-ipfire
>> +++ b/config/kernel/kernel.config.riscv64-ipfire
>> @@ -230,7 +230,7 @@ CONFIG_VM_EVENT_COUNTERS=y
>> # CONFIG_SLAB is not set
>> CONFIG_SLUB=y
>> # CONFIG_SLOB is not set
>> -CONFIG_SLAB_MERGE_DEFAULT=y
>> +# CONFIG_SLAB_MERGE_DEFAULT is not set
>> CONFIG_SLAB_FREELIST_RANDOM=y
>> CONFIG_SLAB_FREELIST_HARDENED=y
>> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
>> diff --git a/config/kernel/kernel.config.x86_64-ipfire b/config/kernel/kernel.config.x86_64-ipfire
>> index 40975b5fc..d3792cbb7 100644
>> --- a/config/kernel/kernel.config.x86_64-ipfire
>> +++ b/config/kernel/kernel.config.x86_64-ipfire
>> @@ -270,7 +270,7 @@ CONFIG_VM_EVENT_COUNTERS=y
>> # CONFIG_SLAB is not set
>> CONFIG_SLUB=y
>> # CONFIG_SLOB is not set
>> -CONFIG_SLAB_MERGE_DEFAULT=y
>> +# CONFIG_SLAB_MERGE_DEFAULT is not set
>> CONFIG_SLAB_FREELIST_RANDOM=y
>> CONFIG_SLAB_FREELIST_HARDENED=y
>> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
I have no expertise. I would defer to the opinion expressed in the
documentation.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] linux: Do not allow slab caches to be merged
2022-08-06 8:00 ` Peter Müller
2022-08-06 11:41 ` Paul Simmons
@ 2022-08-06 12:05 ` Michael Tremer
1 sibling, 0 replies; 6+ messages in thread
From: Michael Tremer @ 2022-08-06 12:05 UTC (permalink / raw)
To: development
[-- Attachment #1: Type: text/plain, Size: 3594 bytes --]
Hello,
Yes, please turn it on. It will protect other processes from being exploited by an attacker who gained access to the system.
Acked-by: Michael Tremer <michael.tremer(a)ipfire.org>
-Michael
> On 6 Aug 2022, at 09:00, Peter Müller <peter.mueller(a)ipfire.org> wrote:
>
> Hello *,
>
> any vetoes / endorsements of this? :-)
>
> Thanks, and best regards,
> Peter Müller
>
>> From the kernel documentation:
>>
>>> For reduced kernel memory fragmentation, slab caches can be
>>> merged when they share the same size and other characteristics.
>>> This carries a risk of kernel heap overflows being able to
>>> overwrite objects from merged caches (and more easily control
>>> cache layout), which makes such heap attacks easier to exploit
>>> by attackers. By keeping caches unmerged, these kinds of exploits
>>> can usually only damage objects in the same cache. [...]
>>
>> Thus, it is more sane to leave slab merging disabled. KSPP and ClipOS
>> recommend this as well.
>>
>> Signed-off-by: Peter Müller <peter.mueller(a)ipfire.org>
>> ---
>> config/kernel/kernel.config.aarch64-ipfire | 2 +-
>> config/kernel/kernel.config.armv6l-ipfire | 2 +-
>> config/kernel/kernel.config.riscv64-ipfire | 2 +-
>> config/kernel/kernel.config.x86_64-ipfire | 2 +-
>> 4 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/config/kernel/kernel.config.aarch64-ipfire b/config/kernel/kernel.config.aarch64-ipfire
>> index 9232335ff..023c3d5aa 100644
>> --- a/config/kernel/kernel.config.aarch64-ipfire
>> +++ b/config/kernel/kernel.config.aarch64-ipfire
>> @@ -247,7 +247,7 @@ CONFIG_VM_EVENT_COUNTERS=y
>> # CONFIG_SLAB is not set
>> CONFIG_SLUB=y
>> # CONFIG_SLOB is not set
>> -CONFIG_SLAB_MERGE_DEFAULT=y
>> +# CONFIG_SLAB_MERGE_DEFAULT is not set
>> CONFIG_SLAB_FREELIST_RANDOM=y
>> CONFIG_SLAB_FREELIST_HARDENED=y
>> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
>> diff --git a/config/kernel/kernel.config.armv6l-ipfire b/config/kernel/kernel.config.armv6l-ipfire
>> index dc0aee51b..b4587826e 100644
>> --- a/config/kernel/kernel.config.armv6l-ipfire
>> +++ b/config/kernel/kernel.config.armv6l-ipfire
>> @@ -250,7 +250,7 @@ CONFIG_VM_EVENT_COUNTERS=y
>> # CONFIG_SLAB is not set
>> CONFIG_SLUB=y
>> # CONFIG_SLOB is not set
>> -CONFIG_SLAB_MERGE_DEFAULT=y
>> +# CONFIG_SLAB_MERGE_DEFAULT is not set
>> CONFIG_SLAB_FREELIST_RANDOM=y
>> CONFIG_SLAB_FREELIST_HARDENED=y
>> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
>> diff --git a/config/kernel/kernel.config.riscv64-ipfire b/config/kernel/kernel.config.riscv64-ipfire
>> index 0801f4389..fb7cda4dd 100644
>> --- a/config/kernel/kernel.config.riscv64-ipfire
>> +++ b/config/kernel/kernel.config.riscv64-ipfire
>> @@ -230,7 +230,7 @@ CONFIG_VM_EVENT_COUNTERS=y
>> # CONFIG_SLAB is not set
>> CONFIG_SLUB=y
>> # CONFIG_SLOB is not set
>> -CONFIG_SLAB_MERGE_DEFAULT=y
>> +# CONFIG_SLAB_MERGE_DEFAULT is not set
>> CONFIG_SLAB_FREELIST_RANDOM=y
>> CONFIG_SLAB_FREELIST_HARDENED=y
>> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
>> diff --git a/config/kernel/kernel.config.x86_64-ipfire b/config/kernel/kernel.config.x86_64-ipfire
>> index 40975b5fc..d3792cbb7 100644
>> --- a/config/kernel/kernel.config.x86_64-ipfire
>> +++ b/config/kernel/kernel.config.x86_64-ipfire
>> @@ -270,7 +270,7 @@ CONFIG_VM_EVENT_COUNTERS=y
>> # CONFIG_SLAB is not set
>> CONFIG_SLUB=y
>> # CONFIG_SLOB is not set
>> -CONFIG_SLAB_MERGE_DEFAULT=y
>> +# CONFIG_SLAB_MERGE_DEFAULT is not set
>> CONFIG_SLAB_FREELIST_RANDOM=y
>> CONFIG_SLAB_FREELIST_HARDENED=y
>> CONFIG_SHUFFLE_PAGE_ALLOCATOR=y
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-08-06 12:05 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-08-01 17:39 [PATCH] linux: Do not allow slab caches to be merged Peter Müller
2022-08-01 20:19 ` Michael Tremer
2022-08-02 9:50 ` Peter Müller
2022-08-06 8:00 ` Peter Müller
2022-08-06 11:41 ` Paul Simmons
2022-08-06 12:05 ` Michael Tremer
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox