The patch titled
Subject: kfence: allow re-enabling KFENCE after system startup
has been added to the -mm tree. Its filename is
kfence-allow-re-enabling-kfence-after-system-startup.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/kfence-allow-re-enabling-kfence-after-system-startup.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/kfence-allow-re-enabling-kfence-after-system-startup.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Tianchen Ding <dtcccc@xxxxxxxxxxxxxxxxx>
Subject: kfence: allow re-enabling KFENCE after system startup
Patch series "provide the flexibility to enable KFENCE", v2.
This patch (of 2):
If once KFENCE is disabled by:
echo 0 > /sys/module/kfence/parameters/sample_interval
KFENCE could never be re-enabled until next rebooting.
Allow re-enabling it by writing a positive num to sample_interval.
Link: https://lkml.kernel.org/r/20220305144858.17040-2-dtcccc@xxxxxxxxxxxxxxxxx
Signed-off-by: Tianchen Ding <dtcccc@xxxxxxxxxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/kfence/core.c | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)
--- a/mm/kfence/core.c~kfence-allow-re-enabling-kfence-after-system-startup
+++ a/mm/kfence/core.c
@@ -38,14 +38,17 @@
#define KFENCE_WARN_ON(cond) \
({ \
const bool __cond = WARN_ON(cond); \
- if (unlikely(__cond)) \
+ if (unlikely(__cond)) { \
WRITE_ONCE(kfence_enabled, false); \
+ disabled_by_warn = true; \
+ } \
__cond; \
})
/* === Data ================================================================= */
static bool kfence_enabled __read_mostly;
+static bool disabled_by_warn __read_mostly;
unsigned long kfence_sample_interval __read_mostly = CONFIG_KFENCE_SAMPLE_INTERVAL;
EXPORT_SYMBOL_GPL(kfence_sample_interval); /* Export for test modules. */
@@ -55,6 +58,7 @@ EXPORT_SYMBOL_GPL(kfence_sample_interval
#endif
#define MODULE_PARAM_PREFIX "kfence."
+static int kfence_enable_late(void);
static int param_set_sample_interval(const char *val, const struct kernel_param *kp)
{
unsigned long num;
@@ -65,10 +69,11 @@ static int param_set_sample_interval(con
if (!num) /* Using 0 to indicate KFENCE is disabled. */
WRITE_ONCE(kfence_enabled, false);
- else if (!READ_ONCE(kfence_enabled) && system_state != SYSTEM_BOOTING)
- return -EINVAL; /* Cannot (re-)enable KFENCE on-the-fly. */
*((unsigned long *)kp->arg) = num;
+
+ if (num && !READ_ONCE(kfence_enabled) && system_state != SYSTEM_BOOTING)
+ return disabled_by_warn ? -EINVAL : kfence_enable_late();
return 0;
}
@@ -787,6 +792,16 @@ void __init kfence_init(void)
(void *)(__kfence_pool + KFENCE_POOL_SIZE));
}
+static int kfence_enable_late(void)
+{
+ if (!__kfence_pool)
+ return -EINVAL;
+
+ WRITE_ONCE(kfence_enabled, true);
+ queue_delayed_work(system_unbound_wq, &kfence_timer, 0);
+ return 0;
+}
+
void kfence_shutdown_cache(struct kmem_cache *s)
{
unsigned long flags;
_
Patches currently in -mm which might be from dtcccc@xxxxxxxxxxxxxxxxx are
kfence-allow-re-enabling-kfence-after-system-startup.patch
kfence-alloc-kfence_pool-after-system-startup.patch
