From: David Keisar Schmidt <[email protected]>
Hi,
The security improvements for prandom_u32 done in commits c51f8f88d705
from October 2020 and d4150779e60f from May 2022 didn't handle the cases
when prandom_bytes_state() and prandom_u32_state() are used.
Specifically, this weak randomization takes place in three cases:
1. mm/slab.c
2. mm/slab_common.c
3. arch/x86/mm/kaslr.c
The first two invocations (mm/slab.c, mm/slab_common.c) are used to create
randomization in the slab allocator freelists.
This is done to make sure attackers can’t obtain information on the heap state.
The last invocation, inside arch/x86/mm/kaslr.c,
randomizes the virtual address space of kernel memory regions.
Hence, we have added the necessary changes to make those randomizations stronger,
switching prandom_u32 instance to siphash.
Changes since v5:
* Fixed coding style issues in mm/slab and mm/slab_common.
* Deleted irrelevant changes which were appended accidentally in
arch/x86/mm/kaslr.
Changes since v4:
* Changed only the arch/x86/mm/kaslr patch.
In particular, we replaced the use of prandom_bytes_state and
prandom_seed_state with siphash inside arch/x86/mm/kaslr.c.
Changes since v3:
* edited commit messages
Changes since v2:
* edited commit message.
* replaced instances of get_random_u32 with get_random_u32_below
in mm/slab.c, mm/slab_common.c
Regards,
David Keisar Schmidt (3):
mm/slab: Replace invocation of weak PRNG
mm/slab_common: Replace invocation of weak PRNG
arch/x86/mm/kaslr: use siphash instead of prandom_bytes_state
arch/x86/mm/kaslr.c | 21 +++++++++++++++------
mm/slab.c | 29 +++++++++--------------------
mm/slab_common.c | 11 +++--------
3 files changed, 27 insertions(+), 34 deletions(-)
--
2.37.3
On 4/16/23 19:21, [email protected] wrote:
> From: David Keisar Schmidt <[email protected]>
Hi,
btw, the threading of v5 and v6 seems broken, v4 was fine.
I've added the patches 1+2 to slab tree for 6.5 (too late for 6.4 now):
https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab.git/log/?h=slab/for-6.5/prandom
Thanks,
Vlastimil
> Hi,
>
> The security improvements for prandom_u32 done in commits c51f8f88d705
> from October 2020 and d4150779e60f from May 2022 didn't handle the cases
> when prandom_bytes_state() and prandom_u32_state() are used.
>
> Specifically, this weak randomization takes place in three cases:
> 1. mm/slab.c
> 2. mm/slab_common.c
> 3. arch/x86/mm/kaslr.c
>
> The first two invocations (mm/slab.c, mm/slab_common.c) are used to create
> randomization in the slab allocator freelists.
> This is done to make sure attackers can’t obtain information on the heap state.
>
> The last invocation, inside arch/x86/mm/kaslr.c,
> randomizes the virtual address space of kernel memory regions.
> Hence, we have added the necessary changes to make those randomizations stronger,
> switching prandom_u32 instance to siphash.
>
> Changes since v5:
> * Fixed coding style issues in mm/slab and mm/slab_common.
> * Deleted irrelevant changes which were appended accidentally in
> arch/x86/mm/kaslr.
>
> Changes since v4:
> * Changed only the arch/x86/mm/kaslr patch.
> In particular, we replaced the use of prandom_bytes_state and
> prandom_seed_state with siphash inside arch/x86/mm/kaslr.c.
>
> Changes since v3:
> * edited commit messages
>
> Changes since v2:
> * edited commit message.
> * replaced instances of get_random_u32 with get_random_u32_below
> in mm/slab.c, mm/slab_common.c
>
> Regards,
>
>
> David Keisar Schmidt (3):
> mm/slab: Replace invocation of weak PRNG
> mm/slab_common: Replace invocation of weak PRNG
> arch/x86/mm/kaslr: use siphash instead of prandom_bytes_state
>
> arch/x86/mm/kaslr.c | 21 +++++++++++++++------
> mm/slab.c | 29 +++++++++--------------------
> mm/slab_common.c | 11 +++--------
> 3 files changed, 27 insertions(+), 34 deletions(-)
>