Re: [PATCH] kasan: Fix sleeping function called from invalid context in PREEMPT_RT

[Dmitry Vyukov]

On Fri, 1 Apr 2022 at 11:09, Zqiang <qiang1.zhang@xxxxxxxxx> wrote:
>
> BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:46
> in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 1, name: swapper/0
> preempt_count: 1, expected: 0
> ...........
> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.17.1-rt16-yocto-preempt-rt #22
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
> BIOS rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
> Call Trace:
> <TASK>
> dump_stack_lvl+0x60/0x8c
> dump_stack+0x10/0x12
>  __might_resched.cold+0x13b/0x173
> rt_spin_lock+0x5b/0xf0
>  ___cache_free+0xa5/0x180
> qlist_free_all+0x7a/0x160
> per_cpu_remove_cache+0x5f/0x70
> smp_call_function_many_cond+0x4c4/0x4f0
> on_each_cpu_cond_mask+0x49/0xc0
> kasan_quarantine_remove_cache+0x54/0xf0
> kasan_cache_shrink+0x9/0x10
> kmem_cache_shrink+0x13/0x20
> acpi_os_purge_cache+0xe/0x20
> acpi_purge_cached_objects+0x21/0x6d
> acpi_initialize_objects+0x15/0x3b
> acpi_init+0x130/0x5ba
> do_one_initcall+0xe5/0x5b0
> kernel_init_freeable+0x34f/0x3ad
> kernel_init+0x1e/0x140
> ret_from_fork+0x22/0x30
>
> When the kmem_cache_shrink() be called, the IPI was triggered, the
> ___cache_free() is called in IPI interrupt context, the local lock
> or spin lock will be acquired. on PREEMPT_RT kernel, these lock is
> replaced with sleepbale rt spin lock, so the above problem is triggered.
> fix it by migrating the release action from the IPI interrupt context
> to the task context on RT kernel.
>
> Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>
> ---
>  mm/kasan/quarantine.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
> index 08291ed33e93..c26fa6473119 100644
> --- a/mm/kasan/quarantine.c
> +++ b/mm/kasan/quarantine.c
> @@ -90,6 +90,7 @@ static void qlist_move_all(struct qlist_head *from, struct qlist_head *to)
>   */
>  static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine);
>
> +static DEFINE_PER_CPU(struct qlist_head, cpu_shrink_qlist);
>  /* Round-robin FIFO array of batches. */
>  static struct qlist_head global_quarantine[QUARANTINE_BATCHES];
>  static int quarantine_head;
> @@ -311,12 +312,14 @@ static void qlist_move_cache(struct qlist_head *from,
>  static void per_cpu_remove_cache(void *arg)
>  {
>         struct kmem_cache *cache = arg;
> -       struct qlist_head to_free = QLIST_INIT;
> +       struct qlist_head *to_free;
>         struct qlist_head *q;
>
> +       to_free = this_cpu_ptr(&cpu_shrink_qlist);
>         q = this_cpu_ptr(&cpu_quarantine);
> -       qlist_move_cache(q, &to_free, cache);
> -       qlist_free_all(&to_free, cache);
> +       qlist_move_cache(q, to_free, cache);
> +       if (!IS_ENABLED(CONFIG_PREEMPT_RT))
> +               qlist_free_all(to_free, cache);
>  }
>
>  /* Free all quarantined objects belonging to cache. */
> @@ -324,6 +327,7 @@ void kasan_quarantine_remove_cache(struct kmem_cache *cache)
>  {
>         unsigned long flags, i;
>         struct qlist_head to_free = QLIST_INIT;
> +       int cpu;
>
>         /*
>          * Must be careful to not miss any objects that are being moved from
> @@ -334,6 +338,11 @@ void kasan_quarantine_remove_cache(struct kmem_cache *cache)
>          */
>         on_each_cpu(per_cpu_remove_cache, cache, 1);
>
> +       if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
> +               for_each_possible_cpu(cpu)
> +                       qlist_free_all(per_cpu_ptr(&cpu_shrink_qlist, cpu), cache);
> +       }

Hi Zqiang,

This code is not protected by any kind of mutex, right? If so, I think
it can lead to subtle memory corruptions, double-frees and leaks when
several tasks move to/free from cpu_shrink_qlist list.


>         raw_spin_lock_irqsave(&quarantine_lock, flags);
>         for (i = 0; i < QUARANTINE_BATCHES; i++) {
>                 if (qlist_empty(&global_quarantine[i]))