with the Z13 finally back online we tried the KASAN enabled factory kernel
there as well. none of the other crashes we see on the z15 but KASAN triggers this

[216976.545411] ------------[ cut here ]------------
[216976.545448] Stack depot reached limit capacity
[216976.545514] WARNING: CPU: 13 PID: 22981 at lib/stackdepot.c:271 __stack_depot_save+0x5a6/0x5b8
[216976.545561] Modules linked in: algif_hash af_alg af_packet rfkill binfmt_misc nbd kvm drm drm_panel_orientation_quirks i2c_core configfs ip_tables x_tables ext4 mbcache jbd2 dm_service_time dm_multipath fuse squashfs loop virtio_blk dm_mod brd bonding tls qeth_l2 bridge stp llc lcs ctcm fsm dasd_fba_mod dasd_eckd_mod dasd_mod evdev crc32_vx_s390 ghash_s390 prng chacha_s390 libchacha zfcp scsi_transport_fc xts sd_mod scsi_dh_emc scsi_dh_rdac scsi_dh_alua aes_s390 t10_pi des_s390 libdes crc64_rocksoft_generic crc64_rocksoft sha512_s390 sg sha256_s390 crc64 sha1_s390 sha_common scsi_mod qeth qdio ccwgroup scsi_common vfio_ccw mdev vfio_iommu_type1 vfio eadm_sch pkey zcrypt rng_core
[216976.545936] CPU: 13 PID: 22981 Comm: mkfs.ext3 Kdump: loaded Not tainted 6.7.4-1.g19af270-default #1 openSUSE Tumbleweed (unreleased) 2e496a1ebf29e36069d2a1de97d0f181d3690830
[216976.545974] Hardware name: IBM 2964 N63 400 (LPAR)
[216976.545989] Krnl PSW : 0404e00180000000 00000003406e7fb2 (__stack_depot_save+0x5aa/0x5b8)
[216976.546021]            R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:3 CC:2 PM:0 RI:0 EA:3
[216976.546049] Krnl GPRS: 001c000000000027 001c000100000023 0000000000000022 0000000000000004
[216976.546078]            0000000000000001 000000033ff8b938 000000034189bcfc 0400002000000000
[216976.546100]            0000000000000020 0000000082b6f848 000000006ea33377 0000000000000100
[216976.546121]            00000003418b9bb0 0000000000001fff 00000003406e7fae 0000000082b6f738
[216976.546189] Krnl Code: 00000003406e7fa2: c020006258f8       larl    %r2,0000000341333192
                           00000003406e7fa8: c0e5ffb0d6f4       brasl   %r14,000000033fd02d90
                          #00000003406e7fae: af000000           mc      0,0
                          >00000003406e7fb2: a7b90000           lghi    %r11,0
                           00000003406e7fb6: a7f4fee9           brc     15,00000003406e7d88
                           00000003406e7fba: 0707               bcr     0,%r7
                           00000003406e7fbc: 0707               bcr     0,%r7
                           00000003406e7fbe: 0707               bcr     0,%r7
[216976.546457] Call Trace:
[216976.546477]  [<00000003406e7fb2>] __stack_depot_save+0x5aa/0x5b8 
[216976.546507] ([<00000003406e7fae>] __stack_depot_save+0x5a6/0x5b8)
[216976.546537]  [<00000003401b187a>] kasan_save_stack+0x52/0x60 
[216976.546562]  [<00000003401b3e2a>] __kasan_record_aux_stack+0xe2/0x100 
[216976.546587]  [<000000033fd4ede8>] task_work_add+0x98/0x230 
[216976.546614]  [<000000033fd85264>] scheduler_tick+0x14c/0x478 
[216976.546649]  [<000000033fe490f4>] update_process_times+0xec/0xf8 
[216976.546677]  [<000000033fe66c78>] tick_sched_handle+0x88/0xb0 
[216976.546718]  [<000000033fe674c0>] tick_nohz_highres_handler+0x80/0xf8 
[216976.546757]  [<000000033fe4a350>] __hrtimer_run_queues+0x310/0x4f8 
[216976.546793]  [<000000033fe4c352>] hrtimer_interrupt+0x282/0x4e0 
[216976.546817]  [<000000033fc956c4>] do_IRQ+0x7c/0x90 
[216976.546844]  [<000000033fc95d66>] do_irq_async+0xc6/0x160 
[216976.546880]  [<0000000340d3057a>] do_ext_irq+0xda/0x120 
[216976.546909]  [<0000000340d4d7f8>] ext_int_handler+0xd0/0x100 
[216976.546942]  [<00000003401b3ab4>] __asan_load8+0xc/0x98 
[216976.546965]  [<00000003405298dc>] bio_associate_blkg+0x5c/0xb8 
[216976.546995]  [<00000003404d3e34>] bio_init+0x11c/0x1d0 
[216976.547028]  [<00000003404d7784>] bio_alloc_bioset+0x2ec/0x548 
[216976.547055]  [<001bffff8083e29c>] ext4_bio_write_folio+0x884/0xd18 [ext4] 
[216976.547753]  [<001bffff807fb434>] mpage_submit_folio+0xf4/0x1a0 [ext4] 
[216976.548326]  [<001bffff807fbc36>] mpage_map_and_submit_buffers+0x36e/0x578 [ext4] 
[216976.548930]  [<001bffff80808ea6>] ext4_do_writepages+0xdc6/0x15c0 [ext4] 
[216976.549488]  [<001bffff8080995c>] ext4_writepages+0x194/0x2a0 [ext4] 
[216976.550054]  [<000000034009c9c6>] do_writepages+0x11e/0x368 
[216976.550086]  [<00000003400826d2>] filemap_fdatawrite_wbc+0xda/0x118 
[216976.550116]  [<0000000340089900>] __filemap_fdatawrite_range+0xb8/0xd0 
[216976.550145]  [<0000000340089ab0>] file_write_and_wait_range+0x80/0xf0 
[216976.550175]  [<00000003402a2256>] generic_buffers_fsync_noflush+0x66/0x198 
[216976.550208]  [<001bffff807e934e>] ext4_sync_file+0x286/0x5d8 [ext4] 
[216976.550800]  [<000000034028f4a4>] __s390x_sys_fsync+0x6c/0xa0 
[216976.550827]  [<000000033fc88b12>] do_syscall+0x19a/0x1d8 
[216976.550849]  [<0000000340d30350>] __do_syscall+0xd0/0xf8 
[216976.550874]  [<0000000340d4d5a0>] system_call+0x70/0x98 
[216976.550894] Last Breaking-Event-Address:
[216976.550905]  [<00000003406efcd0>] __s390_indirect_jump_r14+0x0/0x10
[216976.550936] Kernel panic - not syncing: kernel: panic_on_warn set ...
[216976.550954] CPU: 13 PID: 22981 Comm: mkfs.ext3 Kdump: loaded Not tainted 6.7.4-1.g19af270-default #1 openSUSE Tumbleweed (unreleased) 2e496a1ebf29e36069d2a1de97d0f181d3690830

uploading crash dumps to ziu:/nfs/Bug[whatevernumberwegethere]