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([45.251.33.107]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c76c65812f4sm19347716a12.25.2026.04.08.09.28.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Apr 2026 09:28:59 -0700 (PDT) From: Mohamad Raizudeen To: dmitry.torokhov@gmail.com Cc: Mohamad Raizudeen , kees@kernel.org, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] Input: serio - fix O(n^2) complexity in serio_unregister_driver() Date: Wed, 8 Apr 2026 21:58:47 +0530 Message-ID: <20260408162849.4639-1-raizudeen.kerneldev@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The current implementation restarts the scan from the beginning after each disconnection(goto start_over) because serio_disconnect_port() may delete the current list entry. This results in O(n^2) worst case behaviour. Replace with a two-phase approach: 1.Collect only top-level ports bound to the driver(skip those whose parent= is also bound to the same driver) into a temporary list. 2.Process each collected port once, moving it back to serio_list first to = maintain invariants expected by serio_destroy_port(). This eliminates the restart loop, reduces complexity from O(n^2) to O(n) and avoids use-after-free by never collecting child ports separately. Signed-off-by: Mohamad Raizudeen --- drivers/input/serio/serio.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) diff --git a/drivers/input/serio/serio.c b/drivers/input/serio/serio.c index 54dd26249b02..46b8faf1a46c 100644 --- a/drivers/input/serio/serio.c +++ b/drivers/input/serio/serio.c @@ -821,22 +821,27 @@ EXPORT_SYMBOL(__serio_register_driver); =20 void serio_unregister_driver(struct serio_driver *drv) { - struct serio *serio; + struct serio *serio, *next; + LIST_HEAD(disconnect_list); + =20 guard(mutex)(&serio_mutex); =20 drv->manual_bind =3D true; /* so serio_find_driver ignores it */ serio_remove_pending_events(drv); =20 -start_over: - list_for_each_entry(serio, &serio_list, node) { - if (serio->drv =3D=3D drv) { - serio_disconnect_port(serio); - serio_find_driver(serio); - /* we could've deleted some ports, restart */ - goto start_over; + /*Collect all ports bound to this driver first*/ + list_for_each_entry_safe(serio, next, &serio_list, node) { + if (serio->drv =3D=3D drv && !(serio->parent && serio->parent->drv =3D= =3D drv)) { + list_move_tail(&serio->node, &disconnect_list); } } +=09 + list_for_each_entry_safe(serio, next, &disconnect_list, node) { + list_move_tail(&serio->node, &serio_list); + serio_disconnect_port(serio); + serio_find_driver(serio); + } =20 driver_unregister(&drv->driver); } --=20 2.43.0