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 <mgor...@techsingularity.net>
---
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 3872bc6ec49d..5d759b20540a 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1773,7 +1773,9 @@
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 83c164aba6e0..4cf33305347a 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 9088d613d519..3a941cc45396 100644
--- a/security/Kconfig.hardening
+++ b/security/Kconfig.hardening
@@ -293,6 +293,14 @@ 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"
--
2.43.0
