Re: [bug?] s390: kernel panic on specification exception: 0006

[Heiko Carstens <hca@xxxxxxxxxxxxx>]

[full quote, and adding Ilya]

On Thu, May 15, 2025 at 07:04:20PM +0000, Ihor Solodrai wrote:
> Hi everyone.
> 
> Stumbled on the following while testing unrelated changes to BPF CI scripts:
> 
>     #353     select_reuseport:OK
>     specification exception: 0006 ilc:2 [#1]SMP
>     Modules linked in: bpf_testmod(OE) [last unloaded: bpf_test_modorder_x(OE)]
>     CPU: 0 UID: 0 PID: 108 Comm: new_name Tainted: G           OE       6.15.0-rc4-g169491540638-dirty #1 NONE
>     Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
>     Hardware name: IBM 8561 LT1 400 (KVM/Linux)
>     Krnl PSW : 0404e00180000000 000001e43ac595e4 (hrtimer_interrupt+0x4/0x2a0)
>                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
>     Krnl GPRS: 7fffffffffffffff 000001e43ac595e0 00000000fff8f200 000001e43c52a0c0
>                00000164c50740d8 0000000000000000 0000000000000000 0000000000000000
>                0000000000000000 0000000000000000 000001643afabe00 0000000000000000
>                000003ff9fbadf98 000001e43b747550 000001e43ab12774 00000000fffdfe68
>     Krnl Code:#000001e43ac595e0: 67756573		mxd	%f7,1395(%r5,%r6)
>               >000001e43ac595e4: 743d696e		unknown
>                000001e43ac595e8: 73303031		unknown
>                000001e43ac595ec: 61652c64		unknown
>                000001e43ac595f0: 65627567		unknown
>                000001e43ac595f4: 2d74		ddr	%f7,%f4
>                000001e43ac595f6: 68726561		ld	%f7,1377(%r2,%r6)
>                000001e43ac595fa: 64733d6f		unknown
>     Call Trace:
>      [<000001e43ac595e4>] hrtimer_interrupt+0x4/0x2a0
>      [<000001e43ab128ca>] do_irq_async+0x5a/0x78
>      [<000001e43b65f694>] do_ext_irq+0xac/0x168
>      [<000001e43b66ae90>] ext_int_handler+0xc8/0xf8
>     Last Breaking-Event-Address:
>      [<000001e43ab08a9e>] clock_comparator_work+0x2e/0x30
>     Kernel panic - not syncing: Fatal exception in interrupt
> 
> This is on the current tip of bpf-next (9325d53fe9ad).
> 
> Job: https://github.com/kernel-patches/vmtest/actions/runs/15051985809/job/42309244372
> You can download full logs from there.
> 
> It only happened once so far, didn't repeat on restart.

Looks like the text section, which contains the hrtimer_interrupt
function, got corrupted, and an ASCII string was written there.
The hexdump above with the corrupted code translates to the following
ASCII text: "guest=ins001ae,debug-threads=o".

Does that ring a bell?