From: Paul Simmons <mbatranch@gmail.com>
To: development@lists.ipfire.org
Subject: Re: [PATCH] linux: Do not allow slab caches to be merged
Date: Sat, 06 Aug 2022 06:41:41 -0500 [thread overview]
Message-ID: <8abca6f7-c000-c9af-61aa-b03cbd3a4196@gmail.com> (raw)
In-Reply-To: <2923c885-66ee-13a8-6197-c67ace8e7853@ipfire.org>
[-- 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.
next prev parent reply other threads:[~2022-08-06 11:41 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-01 17:39 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 [this message]
2022-08-06 12:05 ` Michael Tremer
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