Re: [PATCH v2] debugobjects: stop accessing objects after releasing spinlock

From: Andi Shyti
Date: Tue Oct 10 2023 - 08:10:59 EST

Hi Andrzej,

On Tue, Oct 10, 2023 at 02:02:54PM +0200, Andrzej Hajda wrote:
> On 25.09.2023 15:13, Andrzej Hajda wrote:
> > After spinlock release object can be modified/freed by concurrent thread.
> > Using it in such case is error prone, even for printing object state.
> > To avoid such situation local copy of the object is created if necessary.
> >
> > Signed-off-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>
> > ---
> > v2: add missing switch breaks
> > ---
>
> Ping, any volunteer to review?

ops... sorry... this slipped from my review list. Will look at
it soon

Andi

> Regards
> Andrzej
>
>
>
>
> > lib/debugobjects.c | 206 +++++++++++++++++++++------------------------
> > 1 file changed, 97 insertions(+), 109 deletions(-)
> >
> > diff --git a/lib/debugobjects.c b/lib/debugobjects.c
> > index a517256a270b71..3afff2f668fc1e 100644
> > --- a/lib/debugobjects.c
> > +++ b/lib/debugobjects.c
> > @@ -620,9 +620,8 @@ static void debug_objects_fill_pool(void)
> > static void
> > __debug_object_init(void *addr, const struct debug_obj_descr *descr, int onstack)
> > {
> > - enum debug_obj_state state;
> > struct debug_bucket *db;
> > - struct debug_obj *obj;
> > + struct debug_obj *obj, o;
> > unsigned long flags;
> > debug_objects_fill_pool();
> > @@ -644,23 +643,19 @@ __debug_object_init(void *addr, const struct debug_obj_descr *descr, int onstack
> > case ODEBUG_STATE_INACTIVE:
> > obj->state = ODEBUG_STATE_INIT;
> > break;
> > -
> > - case ODEBUG_STATE_ACTIVE:
> > - state = obj->state;
> > - raw_spin_unlock_irqrestore(&db->lock, flags);
> > - debug_print_object(obj, "init");
> > - debug_object_fixup(descr->fixup_init, addr, state);
> > - return;
> > -
> > - case ODEBUG_STATE_DESTROYED:
> > - raw_spin_unlock_irqrestore(&db->lock, flags);
> > - debug_print_object(obj, "init");
> > - return;
> > default:
> > - break;
> > + o = *obj;
> > + obj = NULL;
> > }
> > raw_spin_unlock_irqrestore(&db->lock, flags);
> > +
> > + if (obj)
> > + return;
> > +
> > + debug_print_object(&o, "init");
> > + if (o.state == ODEBUG_STATE_ACTIVE)
> > + debug_object_fixup(descr->fixup_init, addr, o.state);
> > }
> > /**
> > @@ -700,12 +695,9 @@ EXPORT_SYMBOL_GPL(debug_object_init_on_stack);
> > */
> > int debug_object_activate(void *addr, const struct debug_obj_descr *descr)
> > {
> > - struct debug_obj o = { .object = addr, .state = ODEBUG_STATE_NOTAVAILABLE, .descr = descr };
> > - enum debug_obj_state state;
> > struct debug_bucket *db;
> > - struct debug_obj *obj;
> > + struct debug_obj *obj, o;
> > unsigned long flags;
> > - int ret;
> > if (!debug_objects_enabled)
> > return 0;
> > @@ -717,49 +709,47 @@ int debug_object_activate(void *addr, const struct debug_obj_descr *descr)
> > raw_spin_lock_irqsave(&db->lock, flags);
> > obj = lookup_object_or_alloc(addr, db, descr, false, true);
> > - if (likely(!IS_ERR_OR_NULL(obj))) {
> > - bool print_object = false;
> > -
> > + if (unlikely(!obj)) {
> > + raw_spin_unlock_irqrestore(&db->lock, flags);
> > + debug_objects_oom();
> > + return 0;
> > + } else if (likely(!IS_ERR(obj))) {
> > switch (obj->state) {
> > case ODEBUG_STATE_INIT:
> > case ODEBUG_STATE_INACTIVE:
> > obj->state = ODEBUG_STATE_ACTIVE;
> > - ret = 0;
> > break;
> > -
> > case ODEBUG_STATE_ACTIVE:
> > - state = obj->state;
> > - raw_spin_unlock_irqrestore(&db->lock, flags);
> > - debug_print_object(obj, "activate");
> > - ret = debug_object_fixup(descr->fixup_activate, addr, state);
> > - return ret ? 0 : -EINVAL;
> > -
> > case ODEBUG_STATE_DESTROYED:
> > - print_object = true;
> > - ret = -EINVAL;
> > + o = *obj;
> > + obj = NULL;
> > break;
> > default:
> > - ret = 0;
> > break;
> > }
> > - raw_spin_unlock_irqrestore(&db->lock, flags);
> > - if (print_object)
> > - debug_print_object(obj, "activate");
> > - return ret;
> > + } else {
> > + o.object = addr;
> > + o.state = ODEBUG_STATE_NOTAVAILABLE;
> > + o.descr = descr;
> > + obj = NULL;
> > }
> > raw_spin_unlock_irqrestore(&db->lock, flags);
> > - /* If NULL the allocation has hit OOM */
> > - if (!obj) {
> > - debug_objects_oom();
> > + if (obj)
> > return 0;
> > - }
> > - /* Object is neither static nor tracked. It's not initialized */
> > debug_print_object(&o, "activate");
> > - ret = debug_object_fixup(descr->fixup_activate, addr, ODEBUG_STATE_NOTAVAILABLE);
> > - return ret ? 0 : -EINVAL;
> > +
> > + switch (o.state) {
> > + case ODEBUG_STATE_ACTIVE:
> > + case ODEBUG_STATE_NOTAVAILABLE:
> > + if (debug_object_fixup(descr->fixup_activate, addr, o.state))
> > + return 0;
> > + fallthrough;
> > + default:
> > + return -EINVAL;
> > + }
> > }
> > EXPORT_SYMBOL_GPL(debug_object_activate);
> > @@ -771,9 +761,8 @@ EXPORT_SYMBOL_GPL(debug_object_activate);
> > void debug_object_deactivate(void *addr, const struct debug_obj_descr *descr)
> > {
> > struct debug_bucket *db;
> > - struct debug_obj *obj;
> > + struct debug_obj *obj, o;
> > unsigned long flags;
> > - bool print_object = false;
> > if (!debug_objects_enabled)
> > return;
> > @@ -788,30 +777,29 @@ void debug_object_deactivate(void *addr, const struct debug_obj_descr *descr)
> > case ODEBUG_STATE_INIT:
> > case ODEBUG_STATE_INACTIVE:
> > case ODEBUG_STATE_ACTIVE:
> > - if (!obj->astate)
> > + if (!obj->astate) {
> > obj->state = ODEBUG_STATE_INACTIVE;
> > - else
> > - print_object = true;
> > - break;
> > -
> > + break;
> > + }
> > + fallthrough;
> > case ODEBUG_STATE_DESTROYED:
> > - print_object = true;
> > + o = *obj;
> > + obj = NULL;
> > break;
> > default:
> > break;
> > }
> > + } else {
> > + o.object = addr;
> > + o.state = ODEBUG_STATE_NOTAVAILABLE;
> > + o.descr = descr;
> > + obj = NULL;
> > }
> > raw_spin_unlock_irqrestore(&db->lock, flags);
> > - if (!obj) {
> > - struct debug_obj o = { .object = addr,
> > - .state = ODEBUG_STATE_NOTAVAILABLE,
> > - .descr = descr };
> > + if (!obj)
> > debug_print_object(&o, "deactivate");
> > - } else if (print_object) {
> > - debug_print_object(obj, "deactivate");
> > - }
> > }
> > EXPORT_SYMBOL_GPL(debug_object_deactivate);
> > @@ -822,11 +810,9 @@ EXPORT_SYMBOL_GPL(debug_object_deactivate);
> > */
> > void debug_object_destroy(void *addr, const struct debug_obj_descr *descr)
> > {
> > - enum debug_obj_state state;
> > struct debug_bucket *db;
> > - struct debug_obj *obj;
> > + struct debug_obj *obj, o;
> > unsigned long flags;
> > - bool print_object = false;
> > if (!debug_objects_enabled)
> > return;
> > @@ -836,8 +822,10 @@ void debug_object_destroy(void *addr, const struct debug_obj_descr *descr)
> > raw_spin_lock_irqsave(&db->lock, flags);
> > obj = lookup_object(addr, db);
> > - if (!obj)
> > - goto out_unlock;
> > + if (!obj) {
> > + raw_spin_unlock_irqrestore(&db->lock, flags);
> > + return;
> > + }
> > switch (obj->state) {
> > case ODEBUG_STATE_NONE:
> > @@ -846,22 +834,23 @@ void debug_object_destroy(void *addr, const struct debug_obj_descr *descr)
> > obj->state = ODEBUG_STATE_DESTROYED;
> > break;
> > case ODEBUG_STATE_ACTIVE:
> > - state = obj->state;
> > - raw_spin_unlock_irqrestore(&db->lock, flags);
> > - debug_print_object(obj, "destroy");
> > - debug_object_fixup(descr->fixup_destroy, addr, state);
> > - return;
> > -
> > case ODEBUG_STATE_DESTROYED:
> > - print_object = true;
> > + o = *obj;
> > + obj = NULL;
> > break;
> > default:
> > break;
> > }
> > -out_unlock:
> > +
> > raw_spin_unlock_irqrestore(&db->lock, flags);
> > - if (print_object)
> > - debug_print_object(obj, "destroy");
> > +
> > + if (obj)
> > + return;
> > +
> > + debug_print_object(&o, "destroy");
> > +
> > + if (o.state == ODEBUG_STATE_ACTIVE)
> > + debug_object_fixup(descr->fixup_destroy, addr, o.state);
> > }
> > EXPORT_SYMBOL_GPL(debug_object_destroy);
> > @@ -872,9 +861,8 @@ EXPORT_SYMBOL_GPL(debug_object_destroy);
> > */
> > void debug_object_free(void *addr, const struct debug_obj_descr *descr)
> > {
> > - enum debug_obj_state state;
> > struct debug_bucket *db;
> > - struct debug_obj *obj;
> > + struct debug_obj *obj, o;
> > unsigned long flags;
> > if (!debug_objects_enabled)
> > @@ -885,24 +873,29 @@ void debug_object_free(void *addr, const struct debug_obj_descr *descr)
> > raw_spin_lock_irqsave(&db->lock, flags);
> > obj = lookup_object(addr, db);
> > - if (!obj)
> > - goto out_unlock;
> > + if (!obj) {
> > + raw_spin_unlock_irqrestore(&db->lock, flags);
> > + return;
> > + }
> > switch (obj->state) {
> > case ODEBUG_STATE_ACTIVE:
> > - state = obj->state;
> > - raw_spin_unlock_irqrestore(&db->lock, flags);
> > - debug_print_object(obj, "free");
> > - debug_object_fixup(descr->fixup_free, addr, state);
> > - return;
> > + o = *obj;
> > + obj = NULL;
> > + break;
> > default:
> > hlist_del(&obj->node);
> > - raw_spin_unlock_irqrestore(&db->lock, flags);
> > + }
> > +
> > + raw_spin_unlock_irqrestore(&db->lock, flags);
> > +
> > + if (obj) {
> > free_object(obj);
> > return;
> > }
> > -out_unlock:
> > - raw_spin_unlock_irqrestore(&db->lock, flags);
> > +
> > + debug_print_object(&o, "free");
> > + debug_object_fixup(descr->fixup_free, addr, o.state);
> > }
> > EXPORT_SYMBOL_GPL(debug_object_free);
> > @@ -955,9 +948,8 @@ debug_object_active_state(void *addr, const struct debug_obj_descr *descr,
> > unsigned int expect, unsigned int next)
> > {
> > struct debug_bucket *db;
> > - struct debug_obj *obj;
> > + struct debug_obj *obj, o;
> > unsigned long flags;
> > - bool print_object = false;
> > if (!debug_objects_enabled)
> > return;
> > @@ -970,28 +962,27 @@ debug_object_active_state(void *addr, const struct debug_obj_descr *descr,
> > if (obj) {
> > switch (obj->state) {
> > case ODEBUG_STATE_ACTIVE:
> > - if (obj->astate == expect)
> > + if (obj->astate == expect) {
> > obj->astate = next;
> > - else
> > - print_object = true;
> > - break;
> > -
> > + break;
> > + }
> > + fallthrough;
> > default:
> > - print_object = true;
> > + o = *obj;
> > + obj = NULL;
> > break;
> > }
> > + } else {
> > + o.object = addr;
> > + o.state = ODEBUG_STATE_NOTAVAILABLE;
> > + o.descr = descr;
> > + obj = NULL;
> > }
> > raw_spin_unlock_irqrestore(&db->lock, flags);
> > - if (!obj) {
> > - struct debug_obj o = { .object = addr,
> > - .state = ODEBUG_STATE_NOTAVAILABLE,
> > - .descr = descr };
> > + if (!obj)
> > debug_print_object(&o, "active_state");
> > - } else if (print_object) {
> > - debug_print_object(obj, "active_state");
> > - }
> > }
> > EXPORT_SYMBOL_GPL(debug_object_active_state);
> > @@ -999,11 +990,9 @@ EXPORT_SYMBOL_GPL(debug_object_active_state);
> > static void __debug_check_no_obj_freed(const void *address, unsigned long size)
> > {
> > unsigned long flags, oaddr, saddr, eaddr, paddr, chunks;
> > - const struct debug_obj_descr *descr;
> > - enum debug_obj_state state;
> > struct debug_bucket *db;
> > struct hlist_node *tmp;
> > - struct debug_obj *obj;
> > + struct debug_obj *obj, o;
> > int cnt, objs_checked = 0;
> > saddr = (unsigned long) address;
> > @@ -1026,12 +1015,11 @@ static void __debug_check_no_obj_freed(const void *address, unsigned long size)
> > switch (obj->state) {
> > case ODEBUG_STATE_ACTIVE:
> > - descr = obj->descr;
> > - state = obj->state;
> > + o = *obj;
> > raw_spin_unlock_irqrestore(&db->lock, flags);
> > - debug_print_object(obj, "free");
> > - debug_object_fixup(descr->fixup_free,
> > - (void *) oaddr, state);
> > + debug_print_object(&o, "free");
> > + debug_object_fixup(o.descr->fixup_free,
> > + (void *) oaddr, o.state);
> > goto repeat;
> > default:
> > hlist_del(&obj->node);