lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <514c8a18-0b12-481b-94c2-00cabd5a4a42@redhat.com>
Date: Fri, 22 Nov 2024 13:04:34 -0500
From: Waiman Long <llong@...hat.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Andrey Konovalov <andreyknvl@...il.com>
Cc: Marco Elver <elver@...gle.com>, Peter Zijlstra <peterz@...radead.org>,
 Vlastimil Babka <vbabka@...e.cz>,
 syzbot <syzbot+39f85d612b7c20d8db48@...kaller.appspotmail.com>,
 Liam.Howlett@...cle.com, akpm@...ux-foundation.org, jannh@...gle.com,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 lorenzo.stoakes@...cle.com, syzkaller-bugs@...glegroups.com,
 kasan-dev <kasan-dev@...glegroups.com>,
 Andrey Ryabinin <ryabinin.a.a@...il.com>,
 Alexander Potapenko <glider@...gle.com>, dvyukov@...gle.com,
 vincenzo.frascino@....com, paulmck@...nel.org, frederic@...nel.org,
 neeraj.upadhyay@...nel.org, joel@...lfernandes.org, josh@...htriplett.org,
 boqun.feng@...il.com, urezki@...il.com, rostedt@...dmis.org,
 mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
 qiang.zhang1211@...il.com, mingo@...hat.com, juri.lelli@...hat.com,
 vincent.guittot@...aro.org, dietmar.eggemann@....com, bsegall@...gle.com,
 mgorman@...e.de, vschneid@...hat.com, tj@...nel.org, cl@...ux.com,
 penberg@...nel.org, rientjes@...gle.com, iamjoonsoo.kim@....com,
 Thomas Gleixner <tglx@...utronix.de>, roman.gushchin@...ux.dev,
 42.hyeyoo@...il.com, rcu@...r.kernel.org
Subject: Re: [PATCH v2] kasan: Make kasan_record_aux_stack_noalloc() the
 default behaviour

On 11/22/24 10:54 AM, Sebastian Andrzej Siewior wrote:
> From: Peter Zijlstra <peterz@...radead.org>
>
> 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().
>
> [bigeasy: Dressed the diff as patch. ]
>
> Reported-by: syzbot+39f85d612b7c20d8db48@...kaller.appspotmail.com
> Closes: https://lore.kernel.org/all/67275485.050a0220.3c8d68.0a37.GAE@google.com
> Acked-by: Waiman Long <longman@...hat.com>
> Reviewed-by: Andrey Konovalov <andreyknvl@...il.com>
> Reviewed-by: Marco Elver <elver@...gle.com>
> Fixes: 7cb3007ce2da2 ("kasan: generic: introduce kasan_record_aux_stack_noalloc()")
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---
> v1…v2:
>    - Renamed the patch as per Marco.
>    - Added comment to kasan_record_aux_stack() as per Andrey.
>    - Added fixes tag since Waiman that it is the only user.
>    - Added Marco's quote from the mail to the commit description.
>
>   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        | 18 ++++++------------
>   mm/slub.c                 |  2 +-
>   10 files changed, 14 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..2242249c2d50d 100644
> --- a/mm/kasan/generic.c
> +++ b/mm/kasan/generic.c
> @@ -521,7 +521,11 @@ 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;
> @@ -538,17 +542,7 @@ 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);

LGTM

Reviewed-by: Waiman Long <longman@...hat.com>


Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ