linux-kernel - Re: [PATCH 1/3] mm: security: Move hardened usercopy under 'Kernel hardening options'

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Message-ID: <CAHC9VhS-UNb5LkjsihD1sNnSajpKyHZMym8oPsRMwTepmNpo_g@mail.gmail.com>
Date: Mon, 20 Jan 2025 16:42:54 -0500
From: Paul Moore <paul@...l-moore.com>
To: Mel Gorman <mgorman@...hsingularity.net>
Cc: Kees Cook <kees@...nel.org>, Daniel Micay <danielmicay@...il.com>, 
	linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] mm: security: Move hardened usercopy under 'Kernel
 hardening options'

On Fri, Jan 17, 2025 at 8:39 AM Mel Gorman <mgorman@...hsingularity.net> wrote:
>
> There is a submenu for 'Kernel hardening options' under "Security".
> Move HARDENED_USERCOPY under the hardening options as it is clearly
> related.
>
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
> ---
>  security/Kconfig           | 12 ------------
>  security/Kconfig.hardening | 16 ++++++++++++++++
>  2 files changed, 16 insertions(+), 12 deletions(-)

Agree with Kees' comment regarding "Bounds checking" instead of
"String manipulation", but beyond that this is fine with me.

Acked-by: Paul Moore <paul@...l-moore.com>

> diff --git a/security/Kconfig b/security/Kconfig
> index 28e685f53bd1..fe7346dc4bc3 100644
> --- a/security/Kconfig
> +++ b/security/Kconfig
> @@ -159,18 +159,6 @@ config LSM_MMAP_MIN_ADDR
>           this low address space will need the permission specific to the
>           systems running LSM.
>
> -config HARDENED_USERCOPY
> -       bool "Harden memory copies between kernel and userspace"
> -       imply STRICT_DEVMEM
> -       help
> -         This option checks for obviously wrong memory regions when
> -         copying memory to/from the kernel (via copy_to_user() and
> -         copy_from_user() functions) by rejecting memory ranges that
> -         are larger than the specified heap object, span multiple
> -         separately allocated pages, are not on the process stack,
> -         or are part of the kernel text. This prevents entire classes
> -         of heap overflow exploits and similar kernel memory exposures.
> -
>  config FORTIFY_SOURCE
>         bool "Harden common str/mem functions against buffer overflows"
>         depends on ARCH_HAS_FORTIFY_SOURCE
> diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
> index c9d5ca3d8d08..00e6e2ed0c43 100644
> --- a/security/Kconfig.hardening
> +++ b/security/Kconfig.hardening
> @@ -279,6 +279,22 @@ config ZERO_CALL_USED_REGS
>
>  endmenu
>
> +menu "String manipulation"
> +
> +config HARDENED_USERCOPY
> +       bool "Harden memory copies between kernel and userspace"
> +       imply STRICT_DEVMEM
> +       help
> +         This option checks for obviously wrong memory regions when
> +         copying memory to/from the kernel (via copy_to_user() and
> +         copy_from_user() functions) by rejecting memory ranges that
> +         are larger than the specified heap object, span multiple
> +         separately allocated pages, are not on the process stack,
> +         or are part of the kernel text. This prevents entire classes
> +         of heap overflow exploits and similar kernel memory exposures.
> +
> +endmenu
> +
>  menu "Hardening of kernel data structures"
>
>  config LIST_HARDENED
> --
> 2.43.0
>
>


-- 
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