Allow enabling KFENCE after system startup by allocating its pool via the
page allocator. This provides the flexibility to enable KFENCE even if it
wasn't enabled at boot time.
Signed-off-by: Tianchen Ding <dtcccc@xxxxxxxxxxxxxxxxx>
---
mm/kfence/core.c | 99 ++++++++++++++++++++++++++++++++++++++----------
1 file changed, 78 insertions(+), 21 deletions(-)
diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index caa4e84c8b79..f46d63dd7676 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -96,7 +96,7 @@ static unsigned long kfence_skip_covered_thresh __read_mostly = 75;
module_param_named(skip_covered_thresh, kfence_skip_covered_thresh, ulong, 0644);
/* The pool of pages used for guard pages and objects. */
-char *__kfence_pool __ro_after_init;
+char *__kfence_pool __read_mostly;
EXPORT_SYMBOL(__kfence_pool); /* Export for test modules. */
/*
@@ -537,17 +537,19 @@ static void rcu_guarded_free(struct rcu_head *h)
kfence_guarded_free((void *)meta->addr, meta, false);
}
-static bool __init kfence_init_pool(void)
+/*
+ * Initialization of the KFENCE pool after its allocation.
+ * Returns 0 on success; otherwise returns the address up to
+ * which partial initialization succeeded.
+ */
+static unsigned long kfence_init_pool(void)
{
unsigned long addr = (unsigned long)__kfence_pool;
struct page *pages;
int i;
- if (!__kfence_pool)
- return false;
-
if (!arch_kfence_init_pool())
- goto err;
+ return addr;
pages = virt_to_page(addr);
@@ -565,7 +567,7 @@ static bool __init kfence_init_pool(void)
/* Verify we do not have a compound head page. */
if (WARN_ON(compound_head(&pages[i]) != &pages[i]))
- goto err;
+ return addr;
__SetPageSlab(&pages[i]);
}
@@ -578,7 +580,7 @@ static bool __init kfence_init_pool(void)
*/
for (i = 0; i < 2; i++) {
if (unlikely(!kfence_protect(addr)))
- goto err;
+ return addr;
addr += PAGE_SIZE;
}
@@ -595,7 +597,7 @@ static bool __init kfence_init_pool(void)
/* Protect the right redzone. */
if (unlikely(!kfence_protect(addr + PAGE_SIZE)))
- goto err;
+ return addr;
addr += 2 * PAGE_SIZE;
}
@@ -608,9 +610,21 @@ static bool __init kfence_init_pool(void)
*/
kmemleak_free(__kfence_pool);
- return true;
+ return 0;
+}
+
+static bool __init kfence_init_pool_early(void)
+{
+ unsigned long addr;
+
+ if (!__kfence_pool)
+ return false;
+
+ addr = kfence_init_pool();
+
+ if (!addr)
+ return true;
-err:
/*
* Only release unprotected pages, and do not try to go back and change
* page attributes due to risk of failing to do so as well. If changing
@@ -623,6 +637,22 @@ static bool __init kfence_init_pool(void)
return false;
}
+static bool kfence_init_pool_late(void)
+{
+ unsigned long addr, free_pages;
+
+ addr = kfence_init_pool();
+
+ if (!addr)
+ return true;
+
+ /* Same as above. */
+ free_pages = (KFENCE_POOL_SIZE - (addr - (unsigned long)__kfence_pool)) / PAGE_SIZE;
+ free_contig_range(page_to_pfn(virt_to_page(addr)), free_pages);
+ __kfence_pool = NULL;
+ return false;
+}
+
/* === DebugFS Interface ==================================================== */
static int stats_show(struct seq_file *seq, void *v)
@@ -771,31 +801,58 @@ void __init kfence_alloc_pool(void)
pr_err("failed to allocate pool\n");
}
+static void kfence_init_enable(void)
+{
+ if (!IS_ENABLED(CONFIG_KFENCE_STATIC_KEYS))
+ static_branch_enable(&kfence_allocation_key);
+ WRITE_ONCE(kfence_enabled, true);
+ queue_delayed_work(system_unbound_wq, &kfence_timer, 0);
+ pr_info("initialized - using %lu bytes for %d objects at 0x%p-0x%p\n", KFENCE_POOL_SIZE,
+ CONFIG_KFENCE_NUM_OBJECTS, (void *)__kfence_pool,
+ (void *)(__kfence_pool + KFENCE_POOL_SIZE));
+}
+
void __init kfence_init(void)
{
+ stack_hash_seed = (u32)random_get_entropy();
+
/* Setting kfence_sample_interval to 0 on boot disables KFENCE. */
if (!kfence_sample_interval)
return;
- stack_hash_seed = (u32)random_get_entropy();
- if (!kfence_init_pool()) {
+ if (!kfence_init_pool_early()) {
pr_err("%s failed\n", __func__);
return;
}
- if (!IS_ENABLED(CONFIG_KFENCE_STATIC_KEYS))
- static_branch_enable(&kfence_allocation_key);
- WRITE_ONCE(kfence_enabled, true);
- queue_delayed_work(system_unbound_wq, &kfence_timer, 0);
- pr_info("initialized - using %lu bytes for %d objects at 0x%p-0x%p\n", KFENCE_POOL_SIZE,
- CONFIG_KFENCE_NUM_OBJECTS, (void *)__kfence_pool,
- (void *)(__kfence_pool + KFENCE_POOL_SIZE));
+ kfence_init_enable();
+}
+
+static int kfence_init_late(void)
+{
+ const unsigned long nr_pages = KFENCE_POOL_SIZE / PAGE_SIZE;
+ struct page *pages;
+
+ pages = alloc_contig_pages(nr_pages, GFP_KERNEL, first_online_node, NULL);
+
+ if (!pages)
+ return -ENOMEM;
+
+ __kfence_pool = page_to_virt(pages);
+
+ if (!kfence_init_pool_late()) {
+ pr_err("%s failed\n", __func__);
+ return -EBUSY;
+ }
+
+ kfence_init_enable();
+ return 0;
}
static int kfence_enable_late(void)
{
if (!__kfence_pool)
- return -EINVAL;
+ return kfence_init_late();
WRITE_ONCE(kfence_enabled, true);
queue_delayed_work(system_unbound_wq, &kfence_timer, 0);
--
2.27.0
