WARNING: CPU: 0 PID: 8519 at mm/usercopy.c:83 usercopy_warn+0xac/0xd8'

Issue

• After s390x machine booted, when first time either dbginfo.sh or vmur punch is run, following warning message gets generated:

Dec 17 22:55:38 test.example.com dbginfo.sh[8004]: 2 of 12: Collecting z/VM command output
Dec 17 22:55:38 test.example.com dbginfo.sh[8401]: 3 of 12: Collecting procfs
Dec 17 22:55:38 test.example.com dbginfo.sh[8516]: 4 of 12: Collecting sysfs
Dec 17 22:55:39 test.example.com kernel: ------------[ cut here ]------------
Dec 17 22:55:39 test.example.com kernel: Bad or missing usercopy whitelist? Kernel memory exposure attempt detected from SLUB object 'dma-kmalloc-192' (offset 0, size 144)!
Dec 17 22:55:39 test.example.com kernel: WARNING: CPU: 0 PID: 8519 at mm/usercopy.c:83 usercopy_warn+0xac/0xd8
Dec 17 22:55:39 test.example.com kernel: Modules linked in: binfmt_misc nf_tables nfnetlink zfcp scsi_transport_fc pkey ghash_s390 prng xts aes_s390 des_s390 des_generic sha512_s390 vmur zcrypt_cex4 zcrypt xfs libcrc32c qeth_l2 dasd_fba_mod dasd_eckd_mod dasd_mod lcs qeth ctcm qdio ccwgroup fsm dm_mirror dm_region_hash dm_log dm_mod
Dec 17 22:55:39 test.example.com kernel: CPU: 0 PID: 8519 Comm: dump2tar Kdump: loaded Not tainted 4.18.0-53.el8.s390x #1
Dec 17 22:55:39 test.example.com kernel: Hardware name: IBM 2964 N63 400 (z/VM 6.4.0)
Dec 17 22:55:39 test.example.com kernel: Krnl PSW : 00000000e8c556e9 000000002d5855e8 (usercopy_warn+0xac/0xd8)
Dec 17 22:55:39 test.example.com kernel:            R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3
Dec 17 22:55:39 test.example.com kernel: Krnl GPRS: 0000000000009837 0000000000000006 0000000000000083 0000000000000007
Dec 17 22:55:39 test.example.com kernel:            0000000000000007 000000007737a760 0000000000924484 00000000009d5780
Dec 17 22:55:39 test.example.com kernel:            000003ff7f8ff010 000003ff7f8ff010 000000006e32e8d0 0000000000000000
Dec 17 22:55:39 test.example.com kernel:            000000000091a042 00000000007a29d0 0000000000330358 0000000062903b20
Dec 17 22:55:39 test.example.com kernel: Krnl Code: 000000000033034c: c020002fa09e        larl        %r2,924488
                                                                     0000000000330352: c0e5fff09fbf        brasl        %r14,1442d0
                                                                    #0000000000330358: a7f40001                brc        15,33035a
                                                                    >000000000033035c: eb6ff0c00004        lmg        %r6,%r15,192(%r15)
                                                                     0000000000330362: c0f4002270d8        brcl        15,77e512
                                                                     0000000000330368: c020002fa089        larl        %r2,92447a
                                                                     000000000033036e: a7f4ffd4                brc        15,330316
                                                                     0000000000330372: c030003049c4        larl        %r3,9396fa
Dec 17 22:55:39 test.example.com kernel: Call Trace:
Dec 17 22:55:39 test.example.com kernel: ([<0000000000330358>] usercopy_warn+0xa8/0xd8)
Dec 17 22:55:39 test.example.com kernel:  [<000000000030d70a>] __check_heap_object+0xfa/0x160 
Dec 17 22:55:39 test.example.com kernel:  [<00000000003304e4>] __check_object_size+0x15c/0x1d0 
Dec 17 22:55:39 test.example.com kernel:  [<000000000036782c>] simple_read_from_buffer+0x64/0xb8 
Dec 17 22:55:39 test.example.com kernel:  [<0000000000134bc4>] dbfs_read+0xd4/0x140 
Dec 17 22:55:39 test.example.com kernel:  [<00000000003ec4d4>] full_proxy_read+0x84/0xd8 
Dec 17 22:55:39 test.example.com kernel:  [<0000000000335c9a>] __vfs_read+0x3a/0x180 
Dec 17 22:55:39 test.example.com kernel:  [<0000000000335e6a>] vfs_read+0x8a/0x140 
Dec 17 22:55:39 test.example.com kernel:  [<00000000003364e2>] ksys_read+0x62/0xd0 
Dec 17 22:55:39 test.example.com kernel:  [<000000000077b316>] system_call+0x2aa/0x2c8 
Dec 17 22:55:39 test.example.com kernel: Last Breaking-Event-Address:
Dec 17 22:55:39 test.example.com kernel:  [<0000000000330358>] usercopy_warn+0xa8/0xd8
Dec 17 22:55:39 test.example.com kernel: ---[ end trace 182a8832ac954c7b ]---
Dec 17 22:55:39 test.example.com dbginfo.sh[8521]: 5 of 12: Collecting log files
Dec 17 22:55:39 test.example.com dbginfo.sh[8583]: 6 of 12: Collecting config files
Dec 17 22:55:40 test.example.com dbginfo.sh[8855]: 7 of 12: Collecting osa oat output
Dec 17 22:55:40 test.example.com dbginfo.sh[8883]: 8 of 12: Collecting OpenVSwitch output skipped
Dec 17 22:55:40 test.example.com dbginfo.sh[8885]: 9 of 12: Collecting domain xml files skipped
Dec 17 22:55:40 test.example.com dbginfo.sh[8887]: 10a of 12: Collecting docker container output skipped
Dec 17 22:55:40 test.example.com dbginfo.sh[8889]: 10b of 12: Collecting docker network output skipped
Dec 17 22:55:40 test.example.com dbginfo.sh[8890]: 11 of 12: Collecting nvme output
Dec 17 22:55:40 test.example.com dbginfo.sh[8895]: 12 of 12: Postprocessing
Dec 17 22:55:41 test.example.com dbginfo.sh[8907]: Data collection completed