linux-kernel - [PATCH v6 0/3] Replace invocations of prandom_u32() with get_random

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Message-Id: <20230416172158.13133-1-david.keisarschm@mail.huji.ac.il>
Date:   Sun, 16 Apr 2023 20:21:58 +0300
From:   david.keisarschm@...l.huji.ac.il
To:     linux-kernel@...r.kernel.org
Cc:     Jason@...c4.com, linux-mm@...ck.org, akpm@...ux-foundation.org,
        vbabka@...e.cz, 42.hyeyoo@...il.com, mingo@...hat.com,
        hpa@...or.com, keescook@...omium.org,
        David Keisar Schmidt <david.keisarschm@...l.huji.ac.il>,
        ilay.bahat1@...il.com, aksecurity@...il.com
Subject: [PATCH v6 0/3] Replace invocations of prandom_u32() with get_random_u32() and siphash

From: David Keisar Schmidt <david.keisarschm@...l.huji.ac.il>

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