linux-kernel - Re: [PATCH] mm: use stack_depot_early

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Message-ID: <7506d259-1e07-eb74-332b-c0a9064a4a1b@suse.cz>
Date:   Tue, 17 Jan 2023 08:28:32 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     "zhaoyang.huang" <zhaoyang.huang@...soc.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Nathan Chancellor <nathan@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Zhaoyang Huang <huangzhaoyang@...il.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, ke.wang@...soc.com,
        Mirsad Todorovac <mirsad.todorovac@....unizg.hr>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] mm: use stack_depot_early_init for kmemleak

On 1/17/23 06:59, zhaoyang.huang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> 
> Mirsad report bellow error which caused by stack_depot_init failed in kvcalloc.
> Solve this by having stackdepot use stack_depot_early_init.

This is not ideal because kmemleak can be configured so that it's only
enabled on boot with kmemleak=on and not always.
Please look into stack_depot_want_early_init() as suggested:
https://lore.kernel.org/all/f53653bd-aab1-637e-c034-62761f262a03@suse.cz/

> On 1/4/23 17:08, Mirsad Goran Todorovac wrote:
> I hate to bring bad news again, but there seems to be a problem with the output of /sys/kernel/debug/kmemleak:
> 
> [root@...mtodorov ~]# cat /sys/kernel/debug/kmemleak
> unreferenced object 0xffff951c118568b0 (size 16):
> comm "kworker/u12:2", pid 56, jiffies 4294893952 (age 4356.548s)
>     hex dump (first 16 bytes):
>       6d 65 6d 73 74 69 63 6b 30 00 00 00 00 00 00 00 memstick0.......
>     backtrace:
>  [root@...mtodorov ~]#
>    Apparently, backtrace of called functions on the stack is no longer printed with the list of memory leaks.
>  This appeared on Lenovo desktop 10TX000VCR, with AlmaLinux 8.7 and BIOS version M22KT49A (11/10/2022)
>  and 6.2-rc1 and 6.2-rc2 builds.
>  This worked on 6.1 with the same CONFIG_KMEMLEAK=y and MGLRU enabled on a vanilla mainstream kernel
>  from Mr. Torvalds' tree. I don't know if this is deliberate feature for some reason or a bug.
>  Please find attached the config, lshw and kmemleak output.
> 
> reported-by: Mirsad Todorovac <mirsad.todorovac@....unizg.hr>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> ---
>  lib/Kconfig.debug | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 401ad4b..50cc9f5 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -727,6 +727,7 @@ config DEBUG_KMEMLEAK
>  	select KALLSYMS
>  	select CRC32
>  	select STACKDEPOT
> +	select STACKDEPOT_ALWAYS_INIT
>  	help
>  	  Say Y here if you want to enable the memory leak
>  	  detector. The memory allocation/freeing is traced in a way