From d2132f453e3308adc82ab7c101bd5220a9a34167 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Thu, 23 Jan 2025 22:11:13 +0000 Subject: [PATCH] mm: security: Allow default HARDENED_USERCOPY to be set at compile time HARDENED_USERCOPY defaults to on if enabled at compile time. Allow hardened_usercopy= default to be set at compile time similar to init_on_alloc= and init_on_free=. The intent is that hardening options that can be disabled at runtime can set their default at build time. Signed-off-by: Mel Gorman Link: https://lore.kernel.org/r/20250123221115.19722-3-mgorman@techsingularity.net Signed-off-by: Kees Cook --- Documentation/admin-guide/kernel-parameters.txt | 4 +++- mm/usercopy.c | 3 ++- security/Kconfig.hardening | 8 ++++++++ 3 files changed, 13 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index fb8752b42ec85..41d4cf206ec1b 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1785,7 +1785,9 @@ allocation boundaries as a proactive defense against bounds-checking flaws in the kernel's copy_to_user()/copy_from_user() interface. - on Perform hardened usercopy checks (default). + The default is determined by + CONFIG_HARDENED_USERCOPY_DEFAULT_ON. + on Perform hardened usercopy checks. off Disable hardened usercopy checks. hardlockup_all_cpu_backtrace= diff --git a/mm/usercopy.c b/mm/usercopy.c index 16d63bd010aff..e65a612ce8e87 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -255,7 +255,8 @@ void __check_object_size(const void *ptr, unsigned long n, bool to_user) } EXPORT_SYMBOL(__check_object_size); -static bool enable_checks __initdata = true; +static bool enable_checks __initdata = + IS_ENABLED(CONFIG_HARDENED_USERCOPY_DEFAULT_ON); static int __init parse_hardened_usercopy(char *str) { diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening index 9f1bea733523e..45748379f8963 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -294,6 +294,14 @@ config HARDENED_USERCOPY or are part of the kernel text. This prevents entire classes of heap overflow exploits and similar kernel memory exposures. +config HARDENED_USERCOPY_DEFAULT_ON + bool "Harden memory copies by default" + depends on HARDENED_USERCOPY + default HARDENED_USERCOPY + help + This has the effect of setting "hardened_usercopy=on" on the kernel + command line. This can be disabled with "hardened_usercopy=off". + endmenu menu "Hardening of kernel data structures" -- 2.47.3