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Sun, 15 Mar 2026 07:53:29 -0700 (PDT) MIME-Version: 1.0 References: <6ba903ad-9897-42bb-8c2d-337385cc3746@molgen.mpg.de> <49cdd663-bcbd-48b4-ac38-77ce94ef0c8d@molgen.mpg.de> In-Reply-To: From: Sudip Mukherjee Date: Sun, 15 Mar 2026 14:52:52 +0000 X-Gm-Features: AaiRm50qoW5875jVMg8blrX-fMQiTqfJs8s9vRfUb-tlNoJDYMwZIeq1FVYugT8 Message-ID: Subject: Re: BUG: kernel NULL pointer dereference, address: 0000000000000000 To: =?UTF-8?Q?Uwe_Kleine=2DK=C3=B6nig?= Cc: Paul Menzel , Salvatore Bonaccorso , Sudip Mukherjee , linux-kernel@vger.kernel.org, Andrew Morton , linux-mm@kvack.org, regressions@lists.linux.dev, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Hans de Goede , =?UTF-8?Q?Ilpo_J=C3=A4rvinen?= , benh@debian.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: C5C37180003 X-Stat-Signature: 4xb7nodnk18i6odpfzkmpwdbak4zgftd X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1773586410-886778 X-HE-Meta: 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 JlaBGYVQ 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, 15 Mar 2026 at 00:37, Uwe Kleine-K=C3=B6nig w= rote: > > On Sat, Jan 03, 2026 at 11:33:47AM +0000, Sudip Mukherjee wrote: > > On Sat, Jan 03, 2026 at 12:01:19PM +0600, Paul Menzel wrote: > > > Dear Salvatore, > > > > > > > > > Thank you for the follow-up. > > There are several backtraces, I looked at two of them and both trap at > an address that corresponds to: > > /* > * This has to be run as last thing since init_state may need oth= er > * pardevice fields. -arca > */ > -> port->ops->init_state(par_dev, par_dev->state); > if (!test_and_set_bit(PARPORT_DEVPROC_REGISTERED, &port->devflags= )) { > port->proc_device =3D par_dev; > parport_device_proc_register(par_dev); > } > > > in parport_register_dev_model(). However the trapping machine code > doesn't match the kernel modules of the respective kernels, so that's a > bit strange and I'm unable to tell which of the pointer dereferences > there results in the NULL pointer exception. > > Maybe this is also an instance of the hardware disappearing? At least > port->ops and pardev are non-NULL earlier in that function and all > static initialisations of a struct parport_operations have an > init_state() callback. Thanks for confirming. That is also my understanding that the underlying hardware disappeared and mentioned that in my first reply at https://lore.kernel.org/lkml/CADVatmM_mRnkDX=3DhpUjbyKkZnGynxJfRSujGxm2L= aWWMEL_2ew@mail.gmail.com/#t --=20 Regards Sudip