summaryrefslogtreecommitdiff
path: root/mm/kfence
diff options
context:
space:
mode:
Diffstat (limited to 'mm/kfence')
-rw-r--r--mm/kfence/core.c53
-rw-r--r--mm/kfence/kfence.h1
-rw-r--r--mm/kfence/report.c15
3 files changed, 50 insertions, 19 deletions
diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index c5cb54fc696d..67fc321db79b 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -99,6 +99,10 @@ module_param_cb(sample_interval, &sample_interval_param_ops, &kfence_sample_inte
static unsigned long kfence_skip_covered_thresh __read_mostly = 75;
module_param_named(skip_covered_thresh, kfence_skip_covered_thresh, ulong, 0644);
+/* Allocation burst count: number of excess KFENCE allocations per sample. */
+static unsigned int kfence_burst __read_mostly;
+module_param_named(burst, kfence_burst, uint, 0644);
+
/* If true, use a deferrable timer. */
static bool kfence_deferrable __read_mostly = IS_ENABLED(CONFIG_KFENCE_DEFERRABLE);
module_param_named(deferrable, kfence_deferrable, bool, 0444);
@@ -269,6 +273,13 @@ static inline unsigned long metadata_to_pageaddr(const struct kfence_metadata *m
return pageaddr;
}
+static inline bool kfence_obj_allocated(const struct kfence_metadata *meta)
+{
+ enum kfence_object_state state = READ_ONCE(meta->state);
+
+ return state == KFENCE_OBJECT_ALLOCATED || state == KFENCE_OBJECT_RCU_FREEING;
+}
+
/*
* Update the object's metadata state, including updating the alloc/free stacks
* depending on the state transition.
@@ -278,10 +289,14 @@ metadata_update_state(struct kfence_metadata *meta, enum kfence_object_state nex
unsigned long *stack_entries, size_t num_stack_entries)
{
struct kfence_track *track =
- next == KFENCE_OBJECT_FREED ? &meta->free_track : &meta->alloc_track;
+ next == KFENCE_OBJECT_ALLOCATED ? &meta->alloc_track : &meta->free_track;
lockdep_assert_held(&meta->lock);
+ /* Stack has been saved when calling rcu, skip. */
+ if (READ_ONCE(meta->state) == KFENCE_OBJECT_RCU_FREEING)
+ goto out;
+
if (stack_entries) {
memcpy(track->stack_entries, stack_entries,
num_stack_entries * sizeof(stack_entries[0]));
@@ -297,6 +312,7 @@ metadata_update_state(struct kfence_metadata *meta, enum kfence_object_state nex
track->cpu = raw_smp_processor_id();
track->ts_nsec = local_clock(); /* Same source as printk timestamps. */
+out:
/*
* Pairs with READ_ONCE() in
* kfence_shutdown_cache(),
@@ -502,7 +518,7 @@ static void kfence_guarded_free(void *addr, struct kfence_metadata *meta, bool z
raw_spin_lock_irqsave(&meta->lock, flags);
- if (meta->state != KFENCE_OBJECT_ALLOCATED || meta->addr != (unsigned long)addr) {
+ if (!kfence_obj_allocated(meta) || meta->addr != (unsigned long)addr) {
/* Invalid or double-free, bail out. */
atomic_long_inc(&counters[KFENCE_COUNTER_BUGS]);
kfence_report_error((unsigned long)addr, false, NULL, meta,
@@ -780,7 +796,7 @@ static void kfence_check_all_canary(void)
for (i = 0; i < CONFIG_KFENCE_NUM_OBJECTS; i++) {
struct kfence_metadata *meta = &kfence_metadata[i];
- if (meta->state == KFENCE_OBJECT_ALLOCATED)
+ if (kfence_obj_allocated(meta))
check_canary(meta);
}
}
@@ -827,12 +843,12 @@ static void toggle_allocation_gate(struct work_struct *work)
if (!READ_ONCE(kfence_enabled))
return;
- atomic_set(&kfence_allocation_gate, 0);
+ atomic_set(&kfence_allocation_gate, -kfence_burst);
#ifdef CONFIG_KFENCE_STATIC_KEYS
/* Enable static key, and await allocation to happen. */
static_branch_enable(&kfence_allocation_key);
- wait_event_idle(allocation_wait, atomic_read(&kfence_allocation_gate));
+ wait_event_idle(allocation_wait, atomic_read(&kfence_allocation_gate) > 0);
/* Disable static key and reset timer. */
static_branch_disable(&kfence_allocation_key);
@@ -1006,12 +1022,11 @@ void kfence_shutdown_cache(struct kmem_cache *s)
* the lock will not help, as different critical section
* serialization will have the same outcome.
*/
- if (READ_ONCE(meta->cache) != s ||
- READ_ONCE(meta->state) != KFENCE_OBJECT_ALLOCATED)
+ if (READ_ONCE(meta->cache) != s || !kfence_obj_allocated(meta))
continue;
raw_spin_lock_irqsave(&meta->lock, flags);
- in_use = meta->cache == s && meta->state == KFENCE_OBJECT_ALLOCATED;
+ in_use = meta->cache == s && kfence_obj_allocated(meta);
raw_spin_unlock_irqrestore(&meta->lock, flags);
if (in_use) {
@@ -1052,6 +1067,7 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
unsigned long stack_entries[KFENCE_STACK_DEPTH];
size_t num_stack_entries;
u32 alloc_stack_hash;
+ int allocation_gate;
/*
* Perform size check before switching kfence_allocation_gate, so that
@@ -1080,14 +1096,15 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
if (s->flags & SLAB_SKIP_KFENCE)
return NULL;
- if (atomic_inc_return(&kfence_allocation_gate) > 1)
+ allocation_gate = atomic_inc_return(&kfence_allocation_gate);
+ if (allocation_gate > 1)
return NULL;
#ifdef CONFIG_KFENCE_STATIC_KEYS
/*
* waitqueue_active() is fully ordered after the update of
* kfence_allocation_gate per atomic_inc_return().
*/
- if (waitqueue_active(&allocation_wait)) {
+ if (allocation_gate == 1 && waitqueue_active(&allocation_wait)) {
/*
* Calling wake_up() here may deadlock when allocations happen
* from within timer code. Use an irq_work to defer it.
@@ -1154,11 +1171,19 @@ void __kfence_free(void *addr)
* the object, as the object page may be recycled for other-typed
* objects once it has been freed. meta->cache may be NULL if the cache
* was destroyed.
+ * Save the stack trace here so that reports show where the user freed
+ * the object.
*/
- if (unlikely(meta->cache && (meta->cache->flags & SLAB_TYPESAFE_BY_RCU)))
+ if (unlikely(meta->cache && (meta->cache->flags & SLAB_TYPESAFE_BY_RCU))) {
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&meta->lock, flags);
+ metadata_update_state(meta, KFENCE_OBJECT_RCU_FREEING, NULL, 0);
+ raw_spin_unlock_irqrestore(&meta->lock, flags);
call_rcu(&meta->rcu_head, rcu_guarded_free);
- else
+ } else {
kfence_guarded_free(addr, meta, false);
+ }
}
bool kfence_handle_page_fault(unsigned long addr, bool is_write, struct pt_regs *regs)
@@ -1182,14 +1207,14 @@ bool kfence_handle_page_fault(unsigned long addr, bool is_write, struct pt_regs
int distance = 0;
meta = addr_to_metadata(addr - PAGE_SIZE);
- if (meta && READ_ONCE(meta->state) == KFENCE_OBJECT_ALLOCATED) {
+ if (meta && kfence_obj_allocated(meta)) {
to_report = meta;
/* Data race ok; distance calculation approximate. */
distance = addr - data_race(meta->addr + meta->size);
}
meta = addr_to_metadata(addr + PAGE_SIZE);
- if (meta && READ_ONCE(meta->state) == KFENCE_OBJECT_ALLOCATED) {
+ if (meta && kfence_obj_allocated(meta)) {
/* Data race ok; distance calculation approximate. */
if (!to_report || distance > data_race(meta->addr) - addr)
to_report = meta;
diff --git a/mm/kfence/kfence.h b/mm/kfence/kfence.h
index db87a05047bd..dfba5ea06b01 100644
--- a/mm/kfence/kfence.h
+++ b/mm/kfence/kfence.h
@@ -38,6 +38,7 @@
enum kfence_object_state {
KFENCE_OBJECT_UNUSED, /* Object is unused. */
KFENCE_OBJECT_ALLOCATED, /* Object is currently allocated. */
+ KFENCE_OBJECT_RCU_FREEING, /* Object was allocated, and then being freed by rcu. */
KFENCE_OBJECT_FREED, /* Object was allocated, and then freed. */
};
diff --git a/mm/kfence/report.c b/mm/kfence/report.c
index c509aed326ce..451991a3a8f2 100644
--- a/mm/kfence/report.c
+++ b/mm/kfence/report.c
@@ -16,6 +16,7 @@
#include <linux/sprintf.h>
#include <linux/stacktrace.h>
#include <linux/string.h>
+#include <linux/sched/clock.h>
#include <trace/events/error_report.h>
#include <asm/kfence.h>
@@ -108,11 +109,15 @@ static void kfence_print_stack(struct seq_file *seq, const struct kfence_metadat
const struct kfence_track *track = show_alloc ? &meta->alloc_track : &meta->free_track;
u64 ts_sec = track->ts_nsec;
unsigned long rem_nsec = do_div(ts_sec, NSEC_PER_SEC);
+ u64 interval_nsec = local_clock() - meta->alloc_track.ts_nsec;
+ unsigned long rem_interval_nsec = do_div(interval_nsec, NSEC_PER_SEC);
/* Timestamp matches printk timestamp format. */
- seq_con_printf(seq, "%s by task %d on cpu %d at %lu.%06lus:\n",
- show_alloc ? "allocated" : "freed", track->pid,
- track->cpu, (unsigned long)ts_sec, rem_nsec / 1000);
+ seq_con_printf(seq, "%s by task %d on cpu %d at %lu.%06lus (%lu.%06lus ago):\n",
+ show_alloc ? "allocated" : meta->state == KFENCE_OBJECT_RCU_FREEING ?
+ "rcu freeing" : "freed", track->pid,
+ track->cpu, (unsigned long)ts_sec, rem_nsec / 1000,
+ (unsigned long)interval_nsec, rem_interval_nsec / 1000);
if (track->num_stack_entries) {
/* Skip allocation/free internals stack. */
@@ -145,7 +150,7 @@ void kfence_print_object(struct seq_file *seq, const struct kfence_metadata *met
kfence_print_stack(seq, meta, true);
- if (meta->state == KFENCE_OBJECT_FREED) {
+ if (meta->state == KFENCE_OBJECT_FREED || meta->state == KFENCE_OBJECT_RCU_FREEING) {
seq_con_printf(seq, "\n");
kfence_print_stack(seq, meta, false);
}
@@ -314,7 +319,7 @@ bool __kfence_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *sla
kpp->kp_slab_cache = meta->cache;
kpp->kp_objp = (void *)meta->addr;
kfence_to_kp_stack(&meta->alloc_track, kpp->kp_stack);
- if (meta->state == KFENCE_OBJECT_FREED)
+ if (meta->state == KFENCE_OBJECT_FREED || meta->state == KFENCE_OBJECT_RCU_FREEING)
kfence_to_kp_stack(&meta->free_track, kpp->kp_free_stack);
/* get_stack_skipnr() ensures the first entry is outside allocator. */
kpp->kp_ret = kpp->kp_stack[0];
generated by cgit v1.2.3 (git 2.46.0) at 2025-09-06 22:36:36 +0000