linux-kernel - Re: qemu-arm: zram: mkfs.ext4 : Unable to handle kernel NULL pointer dereference at virtual address 00000140

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Date:   Sun, 12 Jun 2022 20:56:56 +0530
From:   Naresh Kamboju <naresh.kamboju@...aro.org>
To:     Sergey Senozhatsky <senozhatsky@...omium.org>
Cc:     Minchan Kim <minchan@...nel.org>,
        open list <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        linux-block <linux-block@...r.kernel.org>,
        regressions@...ts.linux.dev, Jens Axboe <axboe@...nel.dk>,
        Nitin Gupta <ngupta@...are.org>
Subject: Re: qemu-arm: zram: mkfs.ext4 : Unable to handle kernel NULL pointer
 dereference at virtual address 00000140

Hi Sergey,

On Wed, 8 Jun 2022 at 13:06, Sergey Senozhatsky
<senozhatsky@...omium.org> wrote:
>
> On (22/06/08 11:45), Sergey Senozhatsky wrote:
> >
> > Something like this?
>
> May be even something like below. Move static initializer to cpu up
> hook.

Thanks for providing a fix patch.
As per your suggestion debug lock enabled.

CONFIG_DEBUG_LOCK_ALLOC=y

I have tested this patch and the reported issue got resolved [1].

Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>
Tested-by: Linux Kernel Functional Testing <lkft@...aro.org>

> ---
>  mm/zsmalloc.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 9152fbde33b5..6d3789d834e2 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -453,9 +453,7 @@ MODULE_ALIAS("zpool-zsmalloc");
>  #endif /* CONFIG_ZPOOL */
>
>  /* per-cpu VM mapping areas for zspage accesses that cross page boundaries */
> -static DEFINE_PER_CPU(struct mapping_area, zs_map_area) = {
> -       .lock   = INIT_LOCAL_LOCK(lock),
> -};
> +static DEFINE_PER_CPU(struct mapping_area, zs_map_area);
>
>  static __maybe_unused int is_first_page(struct page *page)
>  {
> @@ -1113,6 +1111,7 @@ static inline int __zs_cpu_up(struct mapping_area *area)
>         area->vm_buf = kmalloc(ZS_MAX_ALLOC_SIZE, GFP_KERNEL);
>         if (!area->vm_buf)
>                 return -ENOMEM;
> +       local_lock_init(&area->lock);
>         return 0;
>  }
>
>
> 2.36.1.255.ge46751e96f-goog

Build artifacts link [2]

--
Linaro LKFT
https://lkft.linaro.org

[1] https://lkft.validation.linaro.org/scheduler/job/5160519#L828
[2] https://builds.tuxbuild.com/2ATpwm83jTe2wlUX33YeTpshh2u/