linux-kernel - BUG: Regression: A Problem with /sys/kernel/debug/kmemleak output: backtrace not printed since 6.2.0-rc1

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Date:   Wed, 4 Jan 2023 17:08:59 +0100
From:   Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
To:     linux-kernel@...r.kernel.org
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org
Subject: BUG: Regression: A Problem with /sys/kernel/debug/kmemleak output:
 backtrace not printed since 6.2.0-rc1

Hi all,

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.

Kind regards,
Mirsad

-- 
Mirsad Goran Todorovac
Sistem inženjer
Grafički fakultet | Akademija likovnih umjetnosti
Sveučilište u Zagrebu
-- 
System engineer
Faculty of Graphic Arts | Academy of Fine Arts
University of Zagreb, Republic of Croatia

Download attachment "lshw.txt.xz" of type "application/x-xz" (4648 bytes)

Download attachment "dmesg.log.xz" of type "application/x-xz" (17860 bytes)

Download attachment "config-6.2.0-rc1-mglru-kmemlk-nokasan+.xz" of type "application/x-xz" (57112 bytes)

Download attachment "6.2.0-rc1-kmemleak-nobacktrace.log.xz" of type "application/x-xz" (264 bytes)