[PATCH 6.18 547/869] serial: 8250_lpss: do not touch uninitialized line in ehl_serial_exit()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jiri Slaby (SUSE) <jirislaby@kernel.org>

[ Upstream commit 3e3ae95a3d84a6028f37a07ab7ad78bb14689f2e ]

lpss8250_probe() calls lpss->board->exit() on its error path. For the
EHL board, that is ehl_serial_exit() and it does:
serial8250_get_port(lpss->data.line)->dma = NULL;

But when lpss8250_dma_setup() or serial8250_register_8250_port() fails,
lpss->data.line was never assigned. As lpss is kzalloc()ed, line is 0
and ehl_serial_exit() clears the dma pointer of an unrelated port --
serial8250_ports[0], i.e. ttyS0, which is often the console.

Initialize lpss->data.line to -1 in probe and skip the clearing in
ehl_serial_exit() if no port was registered.

Fixes: 5318f70da7e8 ("serial: 8250_lpss: Balance reference count for PCI DMA device")
Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Assisted-by: LLM
Cc: "Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>
Cc: stable@kernel.org
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: linux-serial@vger.kernel.org
Link: https://patch.msgid.link/f389df34aaa538270313ebd4cea75c2baaf46b95.1791873876.git.jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/tty/serial/8250/8250_lpss.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_lpss.c b/drivers/tty/serial/8250/8250_lpss.c
index 776ec1ef29d62..325e587ae2c42 100644
--- a/drivers/tty/serial/8250/8250_lpss.c
+++ b/drivers/tty/serial/8250/8250_lpss.c
@@ -183,9 +183,8 @@ static int ehl_serial_setup(struct lpss8250 *lpss, struct uart_port *port)
 
 static void ehl_serial_exit(struct lpss8250 *lpss)
 {
-	struct uart_8250_port *up = serial8250_get_port(lpss->data.line);
-
-	up->dma = NULL;
+	if (lpss->data.line >= 0)
+		serial8250_get_port(lpss->data.line)->dma = NULL;
 }
 
 #ifdef CONFIG_SERIAL_8250_DMA
@@ -329,6 +328,8 @@ static int lpss8250_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 		return ret;
 
 	lpss->board = (struct lpss8250_board *)id->driver_data;
+	/* for tests in lpss->board->exit() */
+	lpss->data.line = -1;
 
 	memset(&uart, 0, sizeof(struct uart_8250_port));
 
-- 
2.53.0