diff mbox series

sysctl: improve KASLR effectiveness for mmap

Message ID 5e1acef7-1037-f621-0bd5-123519625c50@ipfire.org
State Accepted
Commit ef21f3e49d2998eb4a223c05ef05f169ae99537a
Headers
Series sysctl: improve KASLR effectiveness for mmap |

Commit Message

Peter Müller July 5, 2019, 5:15 a.m. UTC 
  By feeding more random bits into mmap allocation, the
effectiveness of KASLR will be improved, making attacks
trying to bypass address randomisation more difficult.

Changed sysctl values are:

vm.mmap_rnd_bits = 32 (default: 28)
vm.mmap_rnd_compat_bits = 16 (default: 8)

Signed-off-by: Peter Müller <peter.mueller@ipfire.org>
---
 config/etc/sysctl.conf | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Michael Tremer July 5, 2019, 5:17 a.m. UTC | #1 
Hi,

LOL. “Effectiveness” of the KASLR. Do we even have this enabled?

-Michael

> On 4 Jul 2019, at 20:15, Peter Müller <peter.mueller@ipfire.org> wrote:
> 
> By feeding more random bits into mmap allocation, the
> effectiveness of KASLR will be improved, making attacks
> trying to bypass address randomisation more difficult.
> 
> Changed sysctl values are:
> 
> vm.mmap_rnd_bits = 32 (default: 28)
> vm.mmap_rnd_compat_bits = 16 (default: 8)
> 
> Signed-off-by: Peter Müller <peter.mueller@ipfire.org>
> ---
> config/etc/sysctl.conf | 4 ++++
> 1 file changed, 4 insertions(+)
> 
> diff --git a/config/etc/sysctl.conf b/config/etc/sysctl.conf
> index 9a943fffa..5a67f1795 100644
> --- a/config/etc/sysctl.conf
> +++ b/config/etc/sysctl.conf
> @@ -45,6 +45,10 @@ kernel.kptr_restrict = 2
> # Avoid kernel memory address exposures via dmesg.
> kernel.dmesg_restrict = 1
> 
> +# Improve KASLR effectiveness for mmap
> +vm.mmap_rnd_bits = 32
> +vm.mmap_rnd_compat_bits = 16
> +
> # Minimal preemption granularity for CPU-bound tasks:
> # (default: 1 msec#  (1 + ilog(ncpus)), units: nanoseconds)
> kernel.sched_min_granularity_ns = 10000000
> -- 
> 2.16.4
>
Peter Müller July 5, 2019, 5:28 a.m. UTC | #2 
Hello Michael,

> Hi,
> 
> LOL. “Effectiveness” of the KASLR. Do we even have this enabled?
Yes. Words failed me here - and 8 Bits do not leave _that_ much possibilities...

Thanks, and best regards,
Peter Müller
> 
> -Michael
> 
>> On 4 Jul 2019, at 20:15, Peter Müller <peter.mueller@ipfire.org> wrote:
>>
>> By feeding more random bits into mmap allocation, the
>> effectiveness of KASLR will be improved, making attacks
>> trying to bypass address randomisation more difficult.
>>
>> Changed sysctl values are:
>>
>> vm.mmap_rnd_bits = 32 (default: 28)
>> vm.mmap_rnd_compat_bits = 16 (default: 8)
>>
>> Signed-off-by: Peter Müller <peter.mueller@ipfire.org>
>> ---
>> config/etc/sysctl.conf | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/config/etc/sysctl.conf b/config/etc/sysctl.conf
>> index 9a943fffa..5a67f1795 100644
>> --- a/config/etc/sysctl.conf
>> +++ b/config/etc/sysctl.conf
>> @@ -45,6 +45,10 @@ kernel.kptr_restrict = 2
>> # Avoid kernel memory address exposures via dmesg.
>> kernel.dmesg_restrict = 1
>>
>> +# Improve KASLR effectiveness for mmap
>> +vm.mmap_rnd_bits = 32
>> +vm.mmap_rnd_compat_bits = 16
>> +
>> # Minimal preemption granularity for CPU-bound tasks:
>> # (default: 1 msec#  (1 + ilog(ncpus)), units: nanoseconds)
>> kernel.sched_min_granularity_ns = 10000000
>> -- 
>> 2.16.4
>>
>
diff mbox series

Patch

diff --git a/config/etc/sysctl.conf b/config/etc/sysctl.conf
index 9a943fffa..5a67f1795 100644
--- a/config/etc/sysctl.conf
+++ b/config/etc/sysctl.conf
@@ -45,6 +45,10 @@  kernel.kptr_restrict = 2
 # Avoid kernel memory address exposures via dmesg.
 kernel.dmesg_restrict = 1
 
+# Improve KASLR effectiveness for mmap
+vm.mmap_rnd_bits = 32
+vm.mmap_rnd_compat_bits = 16
+
 # Minimal preemption granularity for CPU-bound tasks:
 # (default: 1 msec#  (1 + ilog(ncpus)), units: nanoseconds)
 kernel.sched_min_granularity_ns = 10000000