[PATCH v1 1/1] Kernel Config to make randomize_va_space read-only.

["Lan Zheng (lanzheng)" <lanzheng@cisco.com>]

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From ba2ec52f170a8e69d6c44238bb578f9518a7e3b7 Mon Sep 17 00:00:00 2001

From: lanzheng <lanzheng@cisco.com>

Date: Tue, 23 Feb 2021 22:49:34 -0500

Subject: [PATCH] This patch adds a kernel build config knob that disallows

 changes to the sysctl variable randomize_va_space.It makes harder for

 attacker to disable ASLR and reduces security risks.



Signed-off-by: lanzheng <lanzheng@cisco.com>

Reviewed-by: Yongkui Han <yonhan@cisco.com>

Tested-by: Nirmala Arumugam <niarumug@cisco.com>

---

 kernel/sysctl.c  | 4 ++++

 security/Kconfig | 8 ++++++++

 2 files changed, 12 insertions(+)



diff --git a/kernel/sysctl.c b/kernel/sysctl.c

index c9fbdd848138..2aa9bc8044c7 100644

--- a/kernel/sysctl.c

+++ b/kernel/sysctl.c

@@ -2426,7 +2426,11 @@ static struct ctl_table kern_table[] = {

                .procname       = "randomize_va_space",

                .data           = &randomize_va_space,

                .maxlen         = sizeof(int),

+#if defined(CONFIG_RANDOMIZE_VA_SPACE_READONLY)

+               .mode           = 0444,

+#else

                .mode           = 0644,

+#endif

                .proc_handler   = proc_dointvec,

        },

 #endif

diff --git a/security/Kconfig b/security/Kconfig

index 7561f6f99f1d..18b9dff4648c 100644

--- a/security/Kconfig

+++ b/security/Kconfig

@@ -7,6 +7,14 @@ menu "Security options"



 source "security/keys/Kconfig"



+config RANDOMIZE_VA_SPACE_READONLY

+       bool "Disallow change of randomize_va_space"

+       default y

+       help

+         If you say Y here, /proc/sys/kernel/randomize_va_space can not

+         be changed by any user, including root, this will help prevent

+         disablement of ASLR.

+

 config SECURITY_DMESG_RESTRICT

        bool "Restrict unprivileged access to the kernel syslog"

        default n

--


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