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AJvYcCVsZDjxEZjl0lobL/s/VDw1eyU1KlJAa/r2NbVhhAKVh8KL6i7Bf1hb0ZFtTi94GHU2blF0/WzgJA==@kvack.org X-Gm-Message-State: AOJu0YzhbfsC2CgdIdVFJ5VBpwVZPxa3g0zG3qp4PfOc5N0MBjfQQgHb SKKPhON6+p2Q0haII09EeQGPusZztk2iFzC3uyGDPl3MVbUfQrfzqjwkU/zXdXiMwlCYO7Zpra+ rZBSxuc0Ej+Wlme632DvhAyosZLWMvzI= X-Gm-Gg: ASbGncuZwvhYA0rKbNgKT5PQ/inBDQwhGryF6/YbFcTDOTQI1MihReqZWuhkoCd2q9F qyavPXVtSbNDdKCPZOFxH89nlyET8IH1mKC55SOFhwVrD4YZkmdFemTb6nuTR0fDgTYdsvex33/ ZkGyR4KoR1oueNe5Rnw2FPYpl96H6BixnTRUjQiBjdxwebyl4bci752C6bTb3XDhE6dhos29Qpi 0fBbV/UaFo6rzytRQL+7tAk+w7U+15zL/ZUEi7N693NjIZ/68+ro6zuXuE71SkbuvyM/ig= X-Google-Smtp-Source: AGHT+IFyO9+LGGmFyReTGUumTl17UewEI50V/5adbCYeJcarlzJzMBdYHfN5rbGaM751Bk5kYaq5rOTh2eihB1pVoqo= X-Received: by 2002:a17:907:2d26:b0:b73:8bdb:9608 with SMTP id a640c23a62f3a-b767700c4a4mr2387387366b.2.1764595596886; Mon, 01 Dec 2025 05:26:36 -0800 (PST) MIME-Version: 1.0 References: <6ba903ad-9897-42bb-8c2d-337385cc3746@molgen.mpg.de> In-Reply-To: From: Sudip Mukherjee Date: Mon, 1 Dec 2025 13:25:59 +0000 X-Gm-Features: AWmQ_blqLxd36fmljwIpQgggDAlKEhmUtfAyB3aAfy7nFPBq21RVnlHBcmLukQM Message-ID: Subject: Re: BUG: kernel NULL pointer dereference, address: 0000000000000000 To: Paul Menzel Cc: Sudip Mukherjee , linux-kernel@vger.kernel.org, Andrew Morton , linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: A9D131C0016 X-Stat-Signature: tamuu1qf4drmc58gjgi9xnjuxkmaxu5m X-Rspam-User: X-HE-Tag: 1764595598-136455 X-HE-Meta: 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 F41XXXTe BJrIsP6ggO832sk+Ke/3IvlExbQAfQWW8dz6+yngwezbUbIuPuPR9W2BpjycsiuV51xCTDjJSSDPYASp2yX2mzGvBBA4h27iSB+COwC/mpqEh9F+L0OeLo0rvbkqs58nEAmWtQUAlZGhjnhorme6xc/mURuMoYX72vfszLYVRODXJ+NaqOO1fD6BHLw9DhC+YQVwTV869tkqsfNvb0ZqfeRX5Req6aXKfLzZ4JU/e0H04cezVurqwM2xfumFZnYUWXCN7WjojlJ7t9uDLfTHVe9KH580OvGxqlNGqPs57hH17FPuryhrRIe6IG/uVK1rN4U0NUTA5NFoQT/pgPGiys6UFukx5D92jKESXKdA1FvPBwWJhC+rG92yqQFTomaX2k6Ck X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 27 Nov 2025 at 22:55, Paul Menzel wrote: > > Dear Linux folks, > > > Am 27.11.25 um 19:51 schrieb Paul Menzel: > > > Unfortunately, not reproducible, but starting with Linux 6.18-rc7, I got > > the oops below *once*: > > > > ``` > > Building and booting Linux 6.18.0-rc7-00041-g765e56e41a5a, I got another > oops. > > [ 15.234799] ppdev lp.0: really_probe: driver_sysfs_add failed > [ 15.234852] ------------[ cut here ]------------ > [ 15.234854] refcount_t: addition on 0; use-after-free. > [ 15.234864] WARNING: CPU: 0 PID: 353 at lib/refcount.c:25 > refcount_warn_saturate+0xcd/0xf0 > > Please find the output of `dmesg` attached. > > (It might be related to booting with an USB-C mini-dock connected, but I > do not know yet.) In both cases, it seems the underlying hardware was removed or the module was unloaded while it was still registering. In the first case, 'parport_default_proc_unregister' has been called while parport driver is still checking for all the connected devices and was executing 'lp_attach'. 'parport_default_proc_unregister' will only be called when the parport module is exiting. Same in the second case, 'lp_attach' was still executing and 'ppdev_cleanup' was called. Are you seeing the crash only from v6.18-rc7 onwards? Was v6.18-rc6 or v6.17 ok for you ? -- Regards Sudip