Re: [PATCH 08/32] s390/dis: Improve show_code() output

[Heiko Carstens <hca@linux.ibm.com>]

On Thu, Oct 01, 2026 at 10:48:32AM +0000, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Medium] s390/dis: NULL pointer dereference in get_trap_ip() during early boot crashes
> > +	pgm_check = test_pt_regs_flag(regs, PIF_PGM_CHECK);
> > +	if (pgm_check)
> > +		trapaddr = get_trap_ip(regs);
> 
> [Severity: Medium]
> Could this call to get_trap_ip() cause a NULL pointer dereference during an
> early boot crash?
> 
> If an early boot exception occurs with the transaction abort bit set
> (regs->int_code & 0x200), __do_early_pgm_check() will handle the exception,
> set PIF_PGM_CHECK, and eventually call show_regs() which calls show_code().
> 
> In get_trap_ip(), there is a check for the transaction abort bit:
> 
> arch/s390/kernel/traps.c:get_trap_ip() {
>     ...
>     if (regs->int_code & 0x200)
>         psw.addr = current->thread.trap_tdb.data[3];

This is not possible, since 0x200 is the mask for TX abort evented. Since the
kernel doesn't make use of TX itself, this bit cannot be set for the early
program check handler.