kasan: make kasan_record_aux_stack_noalloc() the default behaviour

kasan_record_aux_stack_noalloc() was introduced to record a stack trace
without allocating memory in the process.  It has been added to callers
which were invoked while a raw_spinlock_t was held.  More and more callers
were identified and changed over time.  Is it a good thing to have this
while functions try their best to do a locklessly setup?  The only
downside of having kasan_record_aux_stack() not allocate any memory is
that we end up without a stacktrace if stackdepot runs out of memory and
at the same stacktrace was not recorded before To quote Marco Elver from
https://lore.kernel.org/all/CANpmjNPmQYJ7pv1N3cuU8cP18u7PP_uoZD8YxwZd4jtbof9nVQ@mail.gmail.com/

| I'd be in favor, it simplifies things. And stack depot should be
| able to replenish its pool sufficiently in the "non-aux" cases
| i.e. regular allocations. Worst case we fail to record some
| aux stacks, but I think that's only really bad if there's a bug
| around one of these allocations. In general the probabilities
| of this being a regression are extremely small [...]

Make the kasan_record_aux_stack_noalloc() behaviour default as
kasan_record_aux_stack().

[[email protected]: dressed the diff as patch]
Link: https://lkml.kernel.org/r/[email protected]
Fixes: 7cb3007 ("kasan: generic: introduce kasan_record_aux_stack_noalloc()")
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
Reported-by: [email protected]
Closes: https://lore.kernel.org/all/[email protected]
Reviewed-by: Andrey Konovalov <[email protected]>
Reviewed-by: Marco Elver <[email protected]>
Reviewed-by: Waiman Long <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Ben Segall <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Dietmar Eggemann <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Hyeonggon Yoo <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Joel Fernandes (Google) <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Josh Triplett <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: Liam R. Howlett <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Neeraj Upadhyay <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: [email protected]
Cc: Tejun Heo <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Uladzislau Rezki (Sony) <[email protected]>
Cc: Valentin Schneider <[email protected]>
Cc: Vincent Guittot <[email protected]>
Cc: Vincenzo Frascino <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Zqiang <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: Peter Zijlstra

include/linux/kasan.h

@@ -491,7 +491,6 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
 void kasan_cache_shrink(struct kmem_cache *cache);
 void kasan_cache_shutdown(struct kmem_cache *cache);
 void kasan_record_aux_stack(void *ptr);
-void kasan_record_aux_stack_noalloc(void *ptr);
 
 #else /* CONFIG_KASAN_GENERIC */
 
@@ -509,7 +508,6 @@ static inline void kasan_cache_create(struct kmem_cache *cache,
 static inline void kasan_cache_shrink(struct kmem_cache *cache) {}
 static inline void kasan_cache_shutdown(struct kmem_cache *cache) {}
 static inline void kasan_record_aux_stack(void *ptr) {}
-static inline void kasan_record_aux_stack_noalloc(void *ptr) {}
 
 #endif /* CONFIG_KASAN_GENERIC */
 

include/linux/task_work.h

@@ -19,9 +19,6 @@ enum task_work_notify_mode {
 	TWA_SIGNAL,
 	TWA_SIGNAL_NO_IPI,
 	TWA_NMI_CURRENT,
-
-	TWA_FLAGS = 0xff00,
-	TWAF_NO_ALLOC = 0x0100,
 };
 
 static inline bool task_work_pending(struct task_struct *task)

kernel/irq_work.c

@@ -147,7 +147,7 @@ bool irq_work_queue_on(struct irq_work *work, int cpu)
 	if (!irq_work_claim(work))
 		return false;
 
-	kasan_record_aux_stack_noalloc(work);
+	kasan_record_aux_stack(work);
 
 	preempt_disable();
 	if (cpu != smp_processor_id()) {

kernel/rcu/tiny.c

@@ -250,7 +250,7 @@ EXPORT_SYMBOL_GPL(poll_state_synchronize_rcu);
 void kvfree_call_rcu(struct rcu_head *head, void *ptr)
 {
 	if (head)
-		kasan_record_aux_stack_noalloc(ptr);
+		kasan_record_aux_stack(ptr);
 
 	__kvfree_call_rcu(head, ptr);
 }

kernel/rcu/tree.c

@@ -3083,7 +3083,7 @@ __call_rcu_common(struct rcu_head *head, rcu_callback_t func, bool lazy_in)
 	}
 	head->func = func;
 	head->next = NULL;
-	kasan_record_aux_stack_noalloc(head);
+	kasan_record_aux_stack(head);
 	local_irq_save(flags);
 	rdp = this_cpu_ptr(&rcu_data);
 	lazy = lazy_in && !rcu_async_should_hurry();
@@ -3817,7 +3817,7 @@ void kvfree_call_rcu(struct rcu_head *head, void *ptr)
 		return;
 	}
 
-	kasan_record_aux_stack_noalloc(ptr);
+	kasan_record_aux_stack(ptr);
 	success = add_ptr_to_bulk_krc_lock(&krcp, &flags, ptr, !head);
 	if (!success) {
 		run_page_cache_worker(krcp);

kernel/sched/core.c

@@ -10590,7 +10590,7 @@ void task_tick_mm_cid(struct rq *rq, struct task_struct *curr)
 		return;
 
 	/* No page allocation under rq lock */
-	task_work_add(curr, work, TWA_RESUME | TWAF_NO_ALLOC);
+	task_work_add(curr, work, TWA_RESUME);
 }
 
 void sched_mm_cid_exit_signals(struct task_struct *t)

kernel/task_work.c

@@ -55,26 +55,14 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
 		  enum task_work_notify_mode notify)
 {
 	struct callback_head *head;
-	int flags = notify & TWA_FLAGS;
 
-	notify &= ~TWA_FLAGS;
 	if (notify == TWA_NMI_CURRENT) {
 		if (WARN_ON_ONCE(task != current))
 			return -EINVAL;
 		if (!IS_ENABLED(CONFIG_IRQ_WORK))
 			return -EINVAL;
 	} else {
-		/*
-		 * Record the work call stack in order to print it in KASAN
-		 * reports.
-		 *
-		 * Note that stack allocation can fail if TWAF_NO_ALLOC flag
-		 * is set and new page is needed to expand the stack buffer.
-		 */
-		if (flags & TWAF_NO_ALLOC)
-			kasan_record_aux_stack_noalloc(work);
-		else
-			kasan_record_aux_stack(work);
+		kasan_record_aux_stack(work);
 	}
 
 	head = READ_ONCE(task->task_works);

kernel/workqueue.c

@@ -2180,7 +2180,7 @@ static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
 	debug_work_activate(work);
 
 	/* record the work call stack in order to print it in KASAN reports */
-	kasan_record_aux_stack_noalloc(work);
+	kasan_record_aux_stack(work);
 
 	/* we own @work, set data and link */
 	set_work_pwq(work, pwq, extra_flags);

mm/kasan/generic.c

@@ -524,7 +524,11 @@ size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object)
 			sizeof(struct kasan_free_meta) : 0);
 }
 
-static void __kasan_record_aux_stack(void *addr, depot_flags_t depot_flags)
+/*
+ * This function avoids dynamic memory allocations and thus can be called from
+ * contexts that do not allow allocating memory.
+ */
+void kasan_record_aux_stack(void *addr)
 {
 	struct slab *slab = kasan_addr_to_slab(addr);
 	struct kmem_cache *cache;
@@ -541,17 +545,7 @@ static void __kasan_record_aux_stack(void *addr, depot_flags_t depot_flags)
 		return;
 
 	alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0];
-	alloc_meta->aux_stack[0] = kasan_save_stack(0, depot_flags);
-}
-
-void kasan_record_aux_stack(void *addr)
-{
-	return __kasan_record_aux_stack(addr, STACK_DEPOT_FLAG_CAN_ALLOC);
-}
-
-void kasan_record_aux_stack_noalloc(void *addr)
-{
-	return __kasan_record_aux_stack(addr, 0);
+	alloc_meta->aux_stack[0] = kasan_save_stack(0, 0);
 }
 
 void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)

mm/slub.c

@@ -2311,7 +2311,7 @@ bool slab_free_hook(struct kmem_cache *s, void *x, bool init,
 			 * We have to do this manually because the rcu_head is
 			 * not located inside the object.
 			 */
-			kasan_record_aux_stack_noalloc(x);
+			kasan_record_aux_stack(x);
 
 			delayed_free->object = x;
 			call_rcu(&delayed_free->head, slab_free_after_rcu_debug);