Re: [PATCH v2] kasan: add memory corruption identification for software tag-based mode

From: Dmitry Vyukov
Date: Mon Jun 10 2019 - 07:51:34 EST

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On Mon, Jun 10, 2019 at 9:28 AM Walter Wu <walter-zh.wu@xxxxxxxxxxxx> wrote:
>
> On Fri, 2019-06-07 at 21:18 +0800, Dmitry Vyukov wrote:
> > > diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> > > index b40ea104dd36..be0667225b58 100644
> > > --- a/include/linux/kasan.h
> > > +++ b/include/linux/kasan.h
> > > @@ -164,7 +164,11 @@ void kasan_cache_shutdown(struct kmem_cache *cache);
> > >
> > > #else /* CONFIG_KASAN_GENERIC */
> > >
> > > +#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
> > > +void kasan_cache_shrink(struct kmem_cache *cache);
> > > +#else
> >
> > Please restructure the code so that we don't duplicate this function
> > name 3 times in this header.
> >
> We have fixed it, Thank you for your reminder.
>
>
> > > static inline void kasan_cache_shrink(struct kmem_cache *cache) {}
> > > +#endif
> > > static inline void kasan_cache_shutdown(struct kmem_cache *cache) {}
> > >
> > > #endif /* CONFIG_KASAN_GENERIC */
> > > diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> > > index 9950b660e62d..17a4952c5eee 100644
> > > --- a/lib/Kconfig.kasan
> > > +++ b/lib/Kconfig.kasan
> > > @@ -134,6 +134,15 @@ config KASAN_S390_4_LEVEL_PAGING
> > > to 3TB of RAM with KASan enabled). This options allows to force
> > > 4-level paging instead.
> > >
> > > +config KASAN_SW_TAGS_IDENTIFY
> > > + bool "Enable memory corruption idenitfication"
> >
> > s/idenitfication/identification/
> >
> I should replace my glasses.
>
>
> > > + depends on KASAN_SW_TAGS
> > > + help
> > > + Now tag-based KASAN bug report always shows invalid-access error, This
> > > + options can identify it whether it is use-after-free or out-of-bound.
> > > + This will make it easier for programmers to see the memory corruption
> > > + problem.
> >
> > This description looks like a change description, i.e. it describes
> > the current behavior and how it changes. I think code comments should
> > not have such, they should describe the current state of the things.
> > It should also mention the trade-off, otherwise it raises reasonable
> > questions like "why it's not enabled by default?" and "why do I ever
> > want to not enable it?".
> > I would do something like:
> >
> > This option enables best-effort identification of bug type
> > (use-after-free or out-of-bounds)
> > at the cost of increased memory consumption for object quarantine.
> >
> I totally agree with your comments. Would you think we should try to add the cost?
> It may be that it consumes about 1/128th of available memory at full quarantine usage rate.

Hi,

I don't understand the question. We should not add costs if not
necessary. Or you mean why we should add _docs_ regarding the cost? Or
what?

> > > +
> > > config TEST_KASAN
> > > tristate "Module for testing KASAN for bug detection"
> > > depends on m && KASAN
> > > diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
> > > index 5d1065efbd47..d8540e5070cb 100644
> > > --- a/mm/kasan/Makefile
> > > +++ b/mm/kasan/Makefile
> > > @@ -19,3 +19,4 @@ CFLAGS_tags.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
> > > obj-$(CONFIG_KASAN) := common.o init.o report.o
> > > obj-$(CONFIG_KASAN_GENERIC) += generic.o generic_report.o quarantine.o
> > > obj-$(CONFIG_KASAN_SW_TAGS) += tags.o tags_report.o
> > > +obj-$(CONFIG_KASAN_SW_TAGS_IDENTIFY) += quarantine.o
> > > diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> > > index 80bbe62b16cd..e309fbbee831 100644
> > > --- a/mm/kasan/common.c
> > > +++ b/mm/kasan/common.c
> > > @@ -81,7 +81,7 @@ static inline depot_stack_handle_t save_stack(gfp_t flags)
> > > return depot_save_stack(&trace, flags);
> > > }
> > >
> > > -static inline void set_track(struct kasan_track *track, gfp_t flags)
> > > +void set_track(struct kasan_track *track, gfp_t flags)
> >
> > If you make it non-static, it should get kasan_ prefix. The name is too generic.
> >
> Ok, We will add it into next version.
>
>
> >
> > > {
> > > track->pid = current->pid;
> > > track->stack = save_stack(flags);
> > > @@ -457,7 +457,7 @@ static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
> > > return false;
> > >
> > > set_track(&get_alloc_info(cache, object)->free_track, GFP_NOWAIT);
> > > - quarantine_put(get_free_info(cache, object), cache);
> > > + quarantine_put(get_free_info(cache, tagged_object), cache);
> > >
> > > return IS_ENABLED(CONFIG_KASAN_GENERIC);
> > > }
> > > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> > > index 3e0c11f7d7a1..1be04abe2e0d 100644
> > > --- a/mm/kasan/kasan.h
> > > +++ b/mm/kasan/kasan.h
> > > @@ -98,6 +98,12 @@ struct kasan_alloc_meta {
> > > struct qlist_node {
> > > struct qlist_node *next;
> > > };
> > > +struct qlist_object {
> > > + unsigned long addr;
> > > + unsigned int size;
> > > + struct kasan_track free_track;
> > > + struct qlist_node qnode;
> > > +};
> > > struct kasan_free_meta {
> > > /* This field is used while the object is in the quarantine.
> > > * Otherwise it might be used for the allocator freelist.
> > > @@ -133,11 +139,12 @@ void kasan_report(unsigned long addr, size_t size,
> > > bool is_write, unsigned long ip);
> > > void kasan_report_invalid_free(void *object, unsigned long ip);
> > >
> > > -#if defined(CONFIG_KASAN_GENERIC) && \
> > > - (defined(CONFIG_SLAB) || defined(CONFIG_SLUB))
> > > +#if (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS_IDENTIFY)) \
> > > + && (defined(CONFIG_SLAB) || defined(CONFIG_SLUB))
> > > void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache);
> > > void quarantine_reduce(void);
> > > void quarantine_remove_cache(struct kmem_cache *cache);
> > > +void set_track(struct kasan_track *track, gfp_t flags);
> > > #else
> > > static inline void quarantine_put(struct kasan_free_meta *info,
> > > struct kmem_cache *cache) { }
> > > @@ -151,6 +158,31 @@ void print_tags(u8 addr_tag, const void *addr);
> > >
> > > u8 random_tag(void);
> > >
> > > +#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
> > > +bool quarantine_find_object(void *object,
> > > + struct kasan_track *free_track);
> > > +
> > > +struct qlist_object *qobject_create(struct kasan_free_meta *info,
> > > + struct kmem_cache *cache);
> > > +
> > > +void qobject_free(struct qlist_node *qlink, struct kmem_cache *cache);
> > > +#else
> > > +static inline bool quarantine_find_object(void *object,
> > > + struct kasan_track *free_track)
> > > +{
> > > + return false;
> > > +}
> > > +
> > > +static inline struct qlist_object *qobject_create(struct kasan_free_meta *info,
> > > + struct kmem_cache *cache)
> > > +{
> > > + return NULL;
> > > +}
> > > +
> > > +static inline void qobject_free(struct qlist_node *qlink,
> > > + struct kmem_cache *cache) {}
> > > +#endif
> > > +
> > > #else
> > >
> > > static inline void print_tags(u8 addr_tag, const void *addr) { }
> > > @@ -160,6 +192,20 @@ static inline u8 random_tag(void)
> > > return 0;
> > > }
> > >
> > > +static inline bool quarantine_find_object(void *object,
> >
> >
> > Please restructure the code so that we don't duplicate this function
> > name 3 times in this header.
> >
> We have fixed it.
>
>
> > > + struct kasan_track *free_track)
> > > +{
> > > + return false;
> > > +}
> > > +
> > > +static inline struct qlist_object *qobject_create(struct kasan_free_meta *info,
> > > + struct kmem_cache *cache)
> > > +{
> > > + return NULL;
> > > +}
> > > +
> > > +static inline void qobject_free(struct qlist_node *qlink,
> > > + struct kmem_cache *cache) {}
> > > #endif
> > >
> > > #ifndef arch_kasan_set_tag
> > > diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
> > > index 978bc4a3eb51..43b009659d80 100644
> > > --- a/mm/kasan/quarantine.c
> > > +++ b/mm/kasan/quarantine.c
> > > @@ -61,12 +61,16 @@ static void qlist_init(struct qlist_head *q)
> > > static void qlist_put(struct qlist_head *q, struct qlist_node *qlink,
> > > size_t size)
> > > {
> > > - if (unlikely(qlist_empty(q)))
> > > + struct qlist_node *prev_qlink = q->head;
> > > +
> > > + if (unlikely(qlist_empty(q))) {
> > > q->head = qlink;
> > > - else
> > > - q->tail->next = qlink;
> > > - q->tail = qlink;
> > > - qlink->next = NULL;
> > > + q->tail = qlink;
> > > + qlink->next = NULL;
> > > + } else {
> > > + q->head = qlink;
> > > + qlink->next = prev_qlink;
> > > + }
> > > q->bytes += size;
> > > }
> > >
> > > @@ -121,7 +125,11 @@ static unsigned long quarantine_batch_size;
> > > * Quarantine doesn't support memory shrinker with SLAB allocator, so we keep
> > > * the ratio low to avoid OOM.
> > > */
> > > +#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
> > > +#define QUARANTINE_FRACTION 128
> >
> > Explain in a comment why we use lower value for sw tags mode.
> >
> The comment is below.
> "Tag-based KASAN only stores freed object information rather than the
> object itself. The quarantine in tag-based KASAN only needs less usage
> to achieve the same effect as generic KASAN. So We reduce the
> QUARANTINE_FRACTION value to slim the quarantine"
>
>
> > > +#else
> > > #define QUARANTINE_FRACTION 32
> > > +#endif
> > >
> > > static struct kmem_cache *qlink_to_cache(struct qlist_node *qlink)
> > > {
> > > @@ -139,16 +147,24 @@ static void *qlink_to_object(struct qlist_node *qlink, struct kmem_cache *cache)
> > >
> > > static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache)
> > > {
> > > - void *object = qlink_to_object(qlink, cache);
> > > unsigned long flags;
> > > + struct kmem_cache *obj_cache;
> > > + void *object;
> > >
> > > - if (IS_ENABLED(CONFIG_SLAB))
> > > - local_irq_save(flags);
> > > + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS_IDENTIFY)) {
> > > + qobject_free(qlink, cache);
> > > + } else {
> > > + obj_cache = cache ? cache : qlink_to_cache(qlink);
> > > + object = qlink_to_object(qlink, obj_cache);
> > >
> > > - ___cache_free(cache, object, _THIS_IP_);
> > > + if (IS_ENABLED(CONFIG_SLAB))
> > > + local_irq_save(flags);
> > >
> > > - if (IS_ENABLED(CONFIG_SLAB))
> > > - local_irq_restore(flags);
> > > + ___cache_free(obj_cache, object, _THIS_IP_);
> > > +
> > > + if (IS_ENABLED(CONFIG_SLAB))
> > > + local_irq_restore(flags);
> > > + }
> > > }
> > >
> > > static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache)
> > > @@ -160,11 +176,9 @@ static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache)
> > >
> > > qlink = q->head;
> > > while (qlink) {
> > > - struct kmem_cache *obj_cache =
> > > - cache ? cache : qlink_to_cache(qlink);
> > > struct qlist_node *next = qlink->next;
> > >
> > > - qlink_free(qlink, obj_cache);
> > > + qlink_free(qlink, cache);
> > > qlink = next;
> > > }
> > > qlist_init(q);
> > > @@ -175,6 +189,8 @@ void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache)
> > > unsigned long flags;
> > > struct qlist_head *q;
> > > struct qlist_head temp = QLIST_INIT;
> > > + struct kmem_cache *qobject_cache;
> > > + struct qlist_object *free_obj_info;
> > >
> > > /*
> > > * Note: irq must be disabled until after we move the batch to the
> > > @@ -187,7 +203,19 @@ void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache)
> > > local_irq_save(flags);
> > >
> > > q = this_cpu_ptr(&cpu_quarantine);
> > > - qlist_put(q, &info->quarantine_link, cache->size);
> > > + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS_IDENTIFY)) {
> > > + free_obj_info = qobject_create(info, cache);
> > > + if (!free_obj_info) {
> > > + local_irq_restore(flags);
> > > + return;
> > > + }
> > > +
> > > + qobject_cache = qlink_to_cache(&free_obj_info->qnode);
> > > + qlist_put(q, &free_obj_info->qnode, qobject_cache->size);
> >
> > We could use sizeof(*free_obj_info), which looks simpler. Any reason
> > to do another hop through the cache?
> >
> We originally thought we should store the whole slab usage(including metadata)
> instead of qobject size.
> If we use sizeof(*free_obj_info), then below calculation is incorrect.
> total quarantine size = (totalram_pages() << PAGE_SHIFT) / QUARANTINE_FRACTION
> - QUARANTINE_PERCPU_SIZE*num_online_cpus()

So this is total size which is more precise. I see.

> > > + } else {
> > > + qlist_put(q, &info->quarantine_link, cache->size);
> > > + }
> > > +
> > > if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) {
> > > qlist_move_all(q, &temp);
> > >
> > > @@ -220,7 +248,6 @@ void quarantine_reduce(void)
> > > if (likely(READ_ONCE(quarantine_size) <=
> > > READ_ONCE(quarantine_max_size)))
> > > return;
> > > -
> > > /*
> > > * srcu critical section ensures that quarantine_remove_cache()
> > > * will not miss objects belonging to the cache while they are in our
> > > @@ -327,3 +354,90 @@ void quarantine_remove_cache(struct kmem_cache *cache)
> > >
> > > synchronize_srcu(&remove_cache_srcu);
> > > }
> > > +
> > > +#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
> > > +static noinline bool qlist_find_object(struct qlist_head *from, void *arg)
> > > +{
> > > + struct qlist_node *curr;
> > > + struct qlist_object *curr_obj;
> > > + struct qlist_object *target = (struct qlist_object *)arg;
> > > +
> > > + if (unlikely(qlist_empty(from)))
> > > + return false;
> > > +
> > > + curr = from->head;
> > > + while (curr) {
> > > + struct qlist_node *next = curr->next;
> > > +
> > > + curr_obj = container_of(curr, struct qlist_object, qnode);
> > > + if (unlikely((target->addr >= curr_obj->addr) &&
> > > + (target->addr < (curr_obj->addr + curr_obj->size)))) {
> > > + target->free_track = curr_obj->free_track;
> > > + return true;
> > > + }
> > > +
> > > + curr = next;
> > > + }
> > > + return false;
> > > +}
> > > +
> > > +static noinline int per_cpu_find_object(void *arg)
> > > +{
> > > + struct qlist_head *q;
> > > +
> > > + q = this_cpu_ptr(&cpu_quarantine);
> > > + return qlist_find_object(q, arg);
> > > +}
> > > +
> > > +struct cpumask cpu_allowed_mask __read_mostly;
> > > +
> > > +bool quarantine_find_object(void *addr, struct kasan_track *free_track)
> > > +{
> > > + unsigned long flags;
> > > + bool find = false;
> > > + int cpu, i;
> > > + struct qlist_object target;
> > > +
> > > + target.addr = (unsigned long)addr;
> > > +
> > > + cpumask_copy(&cpu_allowed_mask, cpu_online_mask);
> > > + for_each_cpu(cpu, &cpu_allowed_mask) {
> > > + find = smp_call_on_cpu(cpu, per_cpu_find_object,
> > > + (void *)&target, true);
> > > + if (find) {
> > > + if (free_track)
> > > + *free_track = target.free_track;
> > > + return true;
> > > + }
> > > + }
> > > +
> > > + raw_spin_lock_irqsave(&quarantine_lock, flags);
> > > + for (i = quarantine_tail; i >= 0; i--) {
> > > + if (qlist_empty(&global_quarantine[i]))
> > > + continue;
> > > + find = qlist_find_object(&global_quarantine[i],
> > > + (void *)&target);
> > > + if (find) {
> > > + if (free_track)
> > > + *free_track = target.free_track;
> > > + raw_spin_unlock_irqrestore(&quarantine_lock, flags);
> > > + return true;
> > > + }
> > > + }
> > > + for (i = QUARANTINE_BATCHES-1; i > quarantine_tail; i--) {
> >
> > Find a way to calculate the right index using a single loop, rather
> > that copy-paste the whole loop body to do a small adjustment to index.
> >
> single loop:
>
> for (i = quarantine_tail, j = 1; i != quarantine_tail || j != 2;
> i--) {

I would find the classic loop form easier to follow and then compute
the actual index as necessary.
Something along the following lines:

for (i = 0; i < QUARANTINE_BATCHES; i++) {
idx = quarantine_tail - i;
if (idx < 0)
idx += QUARANTINE_BATCHES;
...

> if (i < 0) {
> i = QUARANTINE_BATCHES;
> j = 2;
> continue;
> }
> if (qlist_empty(&global_quarantine[i]))
> continue;
> find = qlist_find_object(&global_quarantine[i],
> (void *)&target);
> if (find) {
> if (free_track)
> *free_track = target.free_track;
> raw_spin_unlock_irqrestore(&quarantine_lock, flags);
> return true;
> }
> }
>
>
> > > + if (qlist_empty(&global_quarantine[i]))
> > > + continue;
> > > + find = qlist_find_object(&global_quarantine[i],
> > > + (void *)&target);
> > > + if (find) {
> > > + if (free_track)
> > > + *free_track = target.free_track;
> > > + raw_spin_unlock_irqrestore(&quarantine_lock, flags);
> > > + return true;
> > > + }
> > > + }
> > > + raw_spin_unlock_irqrestore(&quarantine_lock, flags);
> > > +
> > > + return false;
> > > +}
> > > +#endif
> > > diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> > > index ca9418fe9232..3cbc24cd3d43 100644
> > > --- a/mm/kasan/report.c
> > > +++ b/mm/kasan/report.c
> > > @@ -150,18 +150,27 @@ static void describe_object_addr(struct kmem_cache *cache, void *object,
> > > }
> > >
> > > static void describe_object(struct kmem_cache *cache, void *object,
> > > - const void *addr)
> > > + const void *tagged_addr)
> > > {
> > > + void *untagged_addr = reset_tag(tagged_addr);
> > > struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
> > > + struct kasan_track free_track;
> > >
> > > if (cache->flags & SLAB_KASAN) {
> > > - print_track(&alloc_info->alloc_track, "Allocated");
> > > - pr_err("\n");
> > > - print_track(&alloc_info->free_track, "Freed");
> > > - pr_err("\n");
> > > + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS_IDENTIFY) &&
> > > + quarantine_find_object((void *)tagged_addr,
> > > + &free_track)) {
> > > + print_track(&free_track, "Freed");
> > > + pr_err("\n");
> > > + } else {
> > > + print_track(&alloc_info->alloc_track, "Allocated");
> > > + pr_err("\n");
> > > + print_track(&alloc_info->free_track, "Freed");
> > > + pr_err("\n");
> > > + }
> > > }
> > >
> > > - describe_object_addr(cache, object, addr);
> > > + describe_object_addr(cache, object, untagged_addr);
> > > }
> > >
> > > static inline bool kernel_or_module_addr(const void *addr)
> > > @@ -180,23 +189,25 @@ static inline bool init_task_stack_addr(const void *addr)
> > > sizeof(init_thread_union.stack));
> > > }
> > >
> > > -static void print_address_description(void *addr)
> > > +static void print_address_description(void *tagged_addr)
> > > {
> > > - struct page *page = addr_to_page(addr);
> > > + void *untagged_addr = reset_tag(tagged_addr);
> > > + struct page *page = addr_to_page(untagged_addr);
> > >
> > > dump_stack();
> > > pr_err("\n");
> > >
> > > if (page && PageSlab(page)) {
> > > struct kmem_cache *cache = page->slab_cache;
> > > - void *object = nearest_obj(cache, page, addr);
> > > + void *object = nearest_obj(cache, page, untagged_addr);
> > >
> > > - describe_object(cache, object, addr);
> > > + describe_object(cache, object, tagged_addr);
> > > }
> > >
> > > - if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
> > > + if (kernel_or_module_addr(untagged_addr) &&
> > > + !init_task_stack_addr(untagged_addr)) {
> > > pr_err("The buggy address belongs to the variable:\n");
> > > - pr_err(" %pS\n", addr);
> > > + pr_err(" %pS\n", untagged_addr);
> > > }
> > >
> > > if (page) {
> > > @@ -314,7 +325,7 @@ void kasan_report(unsigned long addr, size_t size,
> > > pr_err("\n");
> > >
> > > if (addr_has_shadow(untagged_addr)) {
> > > - print_address_description(untagged_addr);
> > > + print_address_description(tagged_addr);
> > > pr_err("\n");
> > > print_shadow_for_address(info.first_bad_addr);
> > > } else {
> > > diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
> > > index 63fca3172659..7804b48f760e 100644
> > > --- a/mm/kasan/tags.c
> > > +++ b/mm/kasan/tags.c
> > > @@ -124,6 +124,53 @@ void check_memory_region(unsigned long addr, size_t size, bool write,
> > > }
> > > }
> > >
> > > +#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
> > > +void kasan_cache_shrink(struct kmem_cache *cache)
> > > +{
> > > + quarantine_remove_cache(cache);
> >
> > This does not look to be necessary. There are no objects from that
> > cache in the quarantine in general. Let's not over-complicate this.
> >
> Ok, we will remove it.
>
> >
> >
> > > +}
> > > +
> > > +struct qlist_object *qobject_create(struct kasan_free_meta *info,
> > > + struct kmem_cache *cache)
> > > +{
> > > + struct qlist_object *qobject_info;
> > > + void *object;
> > > +
> > > + object = ((void *)info) - cache->kasan_info.free_meta_offset;
> > > + qobject_info = kmalloc(sizeof(struct qlist_object), GFP_NOWAIT);
> > > + if (!qobject_info)
> > > + return NULL;
> > > + qobject_info->addr = (unsigned long) object;
> > > + qobject_info->size = cache->object_size;
> > > + set_track(&qobject_info->free_track, GFP_NOWAIT);
> > > +
> > > + return qobject_info;
> > > +}
> > > +
> > > +static struct kmem_cache *qobject_to_cache(struct qlist_object *qobject)
> > > +{
> > > + return virt_to_head_page(qobject)->slab_cache;
> >
> > This looks identical to the existing qlink_to_cache, please use the
> > existing function.
> >
> > > +}
> > > +
> > > +void qobject_free(struct qlist_node *qlink, struct kmem_cache *cache)
> > > +{
> > > + struct qlist_object *qobject = container_of(qlink,
> > > + struct qlist_object, qnode);
> > > + unsigned long flags;
> > > +
> > > + struct kmem_cache *qobject_cache =
> > > + cache ? cache : qobject_to_cache(qobject);
> >
> > I don't understand this part.
> > Will caller ever pass us the right cache? Or cache is always NULL? If
> > it's always NULL, why do we accept it at all?
> 2 call flow at v2.
> a). kmalloc() -> quarantine_reduce() -> qlist_free_all(&to_free, NULL)
> -> qlink_free(qlink, NULL) -> qobject_free(qlink, NULL)
> b). kmem_cache_shrink() -> kasan_cache_shrink(cache) ->
> quarantine_remove_cache() -> qlist_free_all(&to_free, cache); ->
> qlink_free(qlink, cache) -> qobject_free(qlink, cache)
>
> It passes the NULL parameter at flow a.
> It passes the cache of slab at flow b.
>
> We always need calculate the slab cache to If we remove flow b.

Good. Let's do it. The simpler, the better.

> > We also allocate qobjects with kmalloc always, so we must use kfree,
> > why do we even mess with caches?
> >
> We call ___cache_free() to free the qobject instead of kfree(), because
> it should be out of quarantine.

I see. Probably this mismatch worth a comment.

> > > +
> > > + if (IS_ENABLED(CONFIG_SLAB))
> > > + local_irq_save(flags);
> > > +
> > > + ___cache_free(qobject_cache, (void *)qobject, _THIS_IP_);
> > > +
> > > + if (IS_ENABLED(CONFIG_SLAB))
> > > + local_irq_restore(flags);
> > > +}
> > > +#endif
> > > +
> > > #define DEFINE_HWASAN_LOAD_STORE(size) \
> > > void __hwasan_load##size##_noabort(unsigned long addr) \
> > > { \
> > > diff --git a/mm/kasan/tags_report.c b/mm/kasan/tags_report.c
> > > index 8eaf5f722271..63b0b1f381ff 100644
> > > --- a/mm/kasan/tags_report.c
> > > +++ b/mm/kasan/tags_report.c
> > > @@ -36,7 +36,13 @@
> > >
> > > const char *get_bug_type(struct kasan_access_info *info)
> > > {
> > > - return "invalid-access";
> > > + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS_IDENTIFY)) {
> > > + if (quarantine_find_object((void *)info->access_addr, NULL))
> > > + return "use-after-free";
> > > + else
> > > + return "out-of-bounds";
> > > + } else
> > > + return "invalid-access";
> > > }
> > >
> > > void *find_first_bad_addr(void *addr, size_t size)
> > > diff --git a/mm/slub.c b/mm/slub.c
> > > index 1b08fbcb7e61..751429d02846 100644
> > > --- a/mm/slub.c
> > > +++ b/mm/slub.c
> > > @@ -3004,7 +3004,7 @@ static __always_inline void slab_free(struct kmem_cache *s, struct page *page,
> > > do_slab_free(s, page, head, tail, cnt, addr);
> > > }
> > >
> > > -#ifdef CONFIG_KASAN_GENERIC
> > > +#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS_IDENTIFY)
> > > void ___cache_free(struct kmem_cache *cache, void *x, unsigned long addr)
> > > {
> > > do_slab_free(cache, virt_to_head_page(x), x, NULL, 1, addr);

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