On Tue, 19 Nov 2024 at 16:57, Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote: > > From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> The patch title is misleading - it might suggest the opposite of what it's doing. I think this might be clearer: "kasan: Make kasan_record_aux_stack_noalloc() the default behaviour" Which is also more or less what you say below. > 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. Marco Elver said in > https://lore.kernel.org/all/20210913112609.2651084-1-elver@xxxxxxxxxx/ > that this is rare. > > Make the kasan_record_aux_stack_noalloc() behaviour default as > kasan_record_aux_stack(). > > [bigeasy: Dressed the diff as patch. ] > > Reported-by: syzbot+39f85d612b7c20d8db48@xxxxxxxxxxxxxxxxxxxxxxxxx > Closes: https://lore.kernel.org/all/67275485.050a0220.3c8d68.0a37.GAE@xxxxxxxxxx > Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Reviewed-by: Marco Elver <elver@xxxxxxxxxx> As I wrote in https://lore.kernel.org/all/CANpmjNPmQYJ7pv1N3cuU8cP18u7PP_uoZD8YxwZd4jtbof9nVQ@xxxxxxxxxxxxxx/: > 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 [...] Good riddance. Thanks, -- Marco > --- > > Didn't add a Fixes tag, didn't want to put > 7cb3007ce2da2 ("kasan: generic: introduce kasan_record_aux_stack_noalloc()") > > there. > > include/linux/kasan.h | 2 -- > include/linux/task_work.h | 3 --- > kernel/irq_work.c | 2 +- > kernel/rcu/tiny.c | 2 +- > kernel/rcu/tree.c | 4 ++-- > kernel/sched/core.c | 2 +- > kernel/task_work.c | 14 +------------- > kernel/workqueue.c | 2 +- > mm/kasan/generic.c | 14 ++------------ > mm/slub.c | 2 +- > 10 files changed, 10 insertions(+), 37 deletions(-) > > diff --git a/include/linux/kasan.h b/include/linux/kasan.h > index 00a3bf7c0d8f0..1a623818e8b39 100644 > --- a/include/linux/kasan.h > +++ b/include/linux/kasan.h > @@ -488,7 +488,6 @@ 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 */ > > @@ -506,7 +505,6 @@ 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 */ > > diff --git a/include/linux/task_work.h b/include/linux/task_work.h > index 2964171856e00..0646804860ff1 100644 > --- a/include/linux/task_work.h > +++ b/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) > diff --git a/kernel/irq_work.c b/kernel/irq_work.c > index 2f4fb336dda17..73f7e1fd4ab4d 100644 > --- a/kernel/irq_work.c > +++ b/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()) { > diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c > index b3b3ce34df631..4b3f319114650 100644 > --- a/kernel/rcu/tiny.c > +++ b/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); > } > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index b1f883fcd9185..7eae9bd818a90 100644 > --- a/kernel/rcu/tree.c > +++ b/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(); > @@ -3807,7 +3807,7 @@ 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); > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index a1c353a62c568..3717360a940d2 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -10485,7 +10485,7 @@ 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) > diff --git a/kernel/task_work.c b/kernel/task_work.c > index c969f1f26be58..d1efec571a4a4 100644 > --- a/kernel/task_work.c > +++ b/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); > diff --git a/kernel/workqueue.c b/kernel/workqueue.c > index 9949ffad8df09..65b8314b2d538 100644 > --- a/kernel/workqueue.c > +++ b/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); > diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c > index 6310a180278b6..b18b5944997f8 100644 > --- a/mm/kasan/generic.c > +++ b/mm/kasan/generic.c > @@ -521,7 +521,7 @@ 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) > +void kasan_record_aux_stack(void *addr) > { > struct slab *slab = kasan_addr_to_slab(addr); > struct kmem_cache *cache; > @@ -538,17 +538,7 @@ 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) > diff --git a/mm/slub.c b/mm/slub.c > index 5b832512044e3..b8c4bf3fe0d07 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -2300,7 +2300,7 @@ 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); > -- > 2.45.2 >
