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kfence: allow re-enabling KFENCE after system startup

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Patch series "provide the flexibility to enable KFENCE", v3.

If CONFIG_CONTIG_ALLOC is not supported, we fallback to try
alloc_pages_exact().  Allocating pages in this way has limits about
MAX_ORDER (default 11).  So we will not support allocating kfence pool
after system startup with a large KFENCE_NUM_OBJECTS.

When handling failures in kfence_init_pool_late(), we pair
free_pages_exact() to alloc_pages_exact() for compatibility consideration,
though it actually does the same as free_contig_range().

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/20220307074516.6920-1-dtcccc@linux.alibaba.com
Link: https://lkml.kernel.org/r/20220307074516.6920-2-dtcccc@linux.alibaba.com
Signed-off-by: Tianchen Ding <dtcccc@linux.alibaba.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Tianchen Ding 2022-03-22 14:48:10 -07:00 committed by Linus Torvalds
parent 56eb8e9416
commit 698361bca2
1 changed files with 18 additions and 3 deletions
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21
mm/kfence/core.c
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@ -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); /* Export for test modules. */
#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(const char *val, const struct kernel_param
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;