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[2a02:3100:aeaf:bd01:78a0:2a2d:507f:c97c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4954a2edbe4sm223826745e9.12.2026.07.19.09.08.34 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sun, 19 Jul 2026 09:08:35 -0700 (PDT) From: Karl Mehltretter To: Greg Kroah-Hartman , Jiri Slaby Cc: Karl Mehltretter , Frank Li , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, stable@vger.kernel.org Subject: [PATCH 4/4] serial: imx: clear imx_uart_ports[] entry on probe failure and removal Date: Sun, 19 Jul 2026 18:08:12 +0200 Message-Id: <20260719160812.35407-5-kmehltretter@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <20260719160812.35407-1-kmehltretter@gmail.com> References: <20260719160812.35407-1-kmehltretter@gmail.com> Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit imx_uart_probe() stores the port in imx_uart_ports[] before calling uart_add_one_port() because console setup during that call uses the table. The entry remains set if uart_add_one_port() fails. imx_uart_remove() also leaves it set after uart_remove_one_port(). sport is devm-allocated, so a failed probe or unbind frees it while imx_uart_ports[] still points to it. A later sibling probe can register the shared console with the old preferred index and dereference the stale entry in imx_uart_console_setup(). Reproduced on qemu's mcimx6ul-evk by unbinding a sibling UART, unbinding the console UART and rebinding the sibling: BUG: KASAN: slab-use-after-free in imx_uart_console_setup+0xd0/0x3d8 Read of size 4 at addr c49ad9d4 by task init/1 Call trace: ... imx_uart_console_setup from try_enable_preferred_console+0x158/0x1f8 try_enable_preferred_console from register_console+0x1cc/0x80c register_console from serial_core_register_port+0xe58/0xeb0 ... Freed by task 1: ... devres_release_all+0x100/0x18c device_unbind_cleanup+0x38/0xdc device_release_driver_internal+0x230/0x288 unbind_store+0x64/0xa8 ... The entry must remain visible while uart_add_one_port() and uart_remove_one_port() run. Clear it when adding the port fails and after removing the port. Save the line index before removal because the uart_port is no longer valid afterward. The probe-failure cleanup relies on the preceding serial-core change "serial: core: do fallible allocations before the console can be registered", which ensures that uart_add_one_port() cannot fail after registering the console. For complete coverage, both changes should be backported together. Fixes: dbff4e9ea2e8 ("IMX UART: remove statically initialized tables") Fixes: 9f322ad064f9 ("imx: serial: handle initialisation failure correctly") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-fable-5 Signed-off-by: Karl Mehltretter --- drivers/tty/serial/imx.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 251a50c8aa38..617c35772056 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -2637,6 +2637,8 @@ static int imx_uart_probe(struct platform_device *pdev) platform_set_drvdata(pdev, sport); ret = uart_add_one_port(&imx_uart_uart_driver, &sport->port); + if (ret) + imx_uart_ports[sport->port.line] = NULL; err_clk: clk_disable_unprepare(sport->clk_ipg); @@ -2647,8 +2649,10 @@ static int imx_uart_probe(struct platform_device *pdev) static void imx_uart_remove(struct platform_device *pdev) { struct imx_port *sport = platform_get_drvdata(pdev); + unsigned int line = sport->port.line; uart_remove_one_port(&imx_uart_uart_driver, &sport->port); + imx_uart_ports[line] = NULL; } static void imx_uart_restore_context(struct imx_port *sport) -- 2.53.0