linux-kernel - Re: [PATCH 1/2] lib/stackdepot: Bail out in __stack_depot_save() if the stack

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Date:   Thu, 10 Aug 2023 11:53:14 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Xiaolei Wang <xiaolei.wang@...driver.com>, catalin.marinas@....com,
        akpm@...ux-foundation.org, glider@...gle.com, andreyknvl@...il.com,
        zhaoyang.huang@...soc.com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] lib/stackdepot: Bail out in __stack_depot_save() if
 the stack_table is not allocated

On 8/10/23 09:47, Xiaolei Wang wrote:
> The __stack_depot_save() may be used by some subsystems even before
> the stack depot is initialized.

Does that currently happen, or only after patch 2/2 it starts happening via
kmemleak?

> So add a check of stack_table in
> __stack_depot_save() to make sure no oops in this case.
> 
> Fixes: 56a61617dd22 ("mm: use stack_depot for recording kmemleak's backtrace")

In case it's only after 2/2 I don't think this is truly "Fixes"?

> Signed-off-by: Xiaolei Wang <xiaolei.wang@...driver.com>
> ---
>  lib/stackdepot.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/stackdepot.c b/lib/stackdepot.c
> index 2f5aa851834e..a0651d013a0d 100644
> --- a/lib/stackdepot.c
> +++ b/lib/stackdepot.c
> @@ -376,7 +376,7 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
>  	 */
>  	nr_entries = filter_irq_stacks(entries, nr_entries);
>  
> -	if (unlikely(nr_entries == 0) || stack_depot_disabled)
> +	if (unlikely(nr_entries == 0) || stack_depot_disabled || unlikely(!stack_table))
>  		goto fast_exit;
>  
>  	hash = hash_stack(entries, nr_entries);