Having slab quarantine without memory erasing is harmful.
If the quarantined objects are not cleaned and contain data, then:
1. they will be useful for use-after-free exploitation,
2. there is no chance to detect use-after-free access.
So we want the quarantined objects to be erased.
Enable init_on_free that cleans objects before placing them into
the quarantine. CONFIG_PAGE_POISONING should be disabled since it
cuts off init_on_free.
Signed-off-by: Alexander Popov <alex.popov@xxxxxxxxx>
---
init/Kconfig | 3 ++-
mm/page_alloc.c | 22 ++++++++++++++++++++++
2 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/init/Kconfig b/init/Kconfig
index 358c8ce818f4..cd4cee71fd4e 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1933,7 +1933,8 @@ config SLAB_FREELIST_HARDENED
config SLAB_QUARANTINE
bool "Enable slab freelist quarantine"
- depends on !KASAN && (SLAB || SLUB)
+ depends on !KASAN && (SLAB || SLUB) && !PAGE_POISONING
+ select INIT_ON_FREE_DEFAULT_ON
help
Enable slab freelist quarantine to delay reusing of freed slab
objects. If this feature is enabled, freed objects are stored
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index fab5e97dc9ca..f67118e88500 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -168,6 +168,27 @@ static int __init early_init_on_alloc(char *buf)
}
early_param("init_on_alloc", early_init_on_alloc);
+#ifdef CONFIG_SLAB_QUARANTINE
+static int __init early_init_on_free(char *buf)
+{
+ /*
+ * Having slab quarantine without memory erasing is harmful.
+ * If the quarantined objects are not cleaned and contain data, then:
+ * 1. they will be useful for use-after-free exploitation,
+ * 2. use-after-free access may not be detected.
+ * So we want the quarantined objects to be erased.
+ *
+ * Enable init_on_free that cleans objects before placing them into
+ * the quarantine. CONFIG_PAGE_POISONING should be disabled since it
+ * cuts off init_on_free.
+ */
+ BUILD_BUG_ON(!IS_ENABLED(CONFIG_INIT_ON_FREE_DEFAULT_ON));
+ BUILD_BUG_ON(IS_ENABLED(CONFIG_PAGE_POISONING));
+ pr_info("mem auto-init: init_on_free is on for CONFIG_SLAB_QUARANTINE\n");
+
+ return 0;
+}
+#else /* CONFIG_SLAB_QUARANTINE */
static int __init early_init_on_free(char *buf)
{
int ret;
@@ -184,6 +205,7 @@ static int __init early_init_on_free(char *buf)
static_branch_disable(&init_on_free);
return ret;
}
+#endif /* CONFIG_SLAB_QUARANTINE */
early_param("init_on_free", early_init_on_free);
/*
--
2.26.2
