Re: [BUG] general protection fault in upd78f0730_tiocmset

[Johan Hovold]

On Fri, Sep 11, 2026 at 01:16:11PM -0700, Farhad Alemi wrote:

> We are reporting the following crash (reproducer attached):
> Linux version 7.3.0-rc2 50d05c7c76c96b90462f24debacca971d2e86713
> Build Config: UpstreamAppArmorKASAN (KASAN + UBSAN, panic_on_warn=1)
> 
> [   44.256596][ T9490] Oops: general protection fault, probably for
> non-canonical address 0xdffffc00000000ba: 0000 [#1] SMP KASAN NOPTI
> [   44.258408][ T9490] KASAN: null-ptr-deref in range
> [0x00000000000005d0-0x00000000000005d7]
> [   44.259206][ T9490] CPU: 0 UID: 0 PID: 9490 Comm: repro Not tainted
> 7.3.0-rc2-00099-g50d05c7c76c9 #1 PREEMPT(full)
> [   44.260235][ T9490] Hardware name: QEMU Standard PC (Q35 + ICH9,
> 2009), BIOS 1.17.0-debian-1.17.0-1ubuntu1 04/01/2014
> [   44.261396][ T9490] RIP: 0010:upd78f0730_tiocmset+0x86/0x4b0

> [   44.270495][ T9490] Call Trace:
> [   44.270882][ T9490]  <TASK>
> [   44.271160][ T9490]  ? __pfx_upd78f0730_tiocmset+0x10/0x10
> [   44.271694][ T9490]  ? __pfx_serial_port_dtr_rts+0x10/0x10
> [   44.272208][ T9490]  tty_port_shutdown+0x165/0x220
> [   44.272672][ T9490]  tty_port_hangup+0xee/0x170
> [   44.273101][ T9490]  ? __pfx_serial_hangup+0x10/0x10
> [   44.273600][ T9490]  __tty_hangup+0x5a7/0x650
> [   44.274074][ T9490]  tty_ioctl+0x757/0xde0

Another symptom of this issue was reported by syzbot a couple of weeks
ago and I posted a fix for the tty layer last week:

	https://lore.kernel.org/lkml/20260910125114.640880-1-johan@xxxxxxxxxx/

Johan