From: Stepan Ionichev <sozdayvek@gmail.com>
To: gregkh@linuxfoundation.org
Cc: jirislaby@kernel.org, linux-serial@vger.kernel.org,
linux-kernel@vger.kernel.org,
Stepan Ionichev <sozdayvek@gmail.com>
Subject: [PATCH] tty: serial: 8250: protect against NULL uart->port.dev in register
Date: Fri, 8 May 2026 23:12:37 +0500 [thread overview]
Message-ID: <20260508181237.11146-1-sozdayvek@gmail.com> (raw)
serial8250_register_8250_port() conditionally copies uart->port.dev
from up->port.dev only when up->port.dev is non-NULL:
if (up->port.dev) {
uart->port.dev = up->port.dev;
...
}
So if both the existing uart slot and up have a NULL ->dev,
uart->port.dev remains NULL. The very next ACPI companion check
then dereferences it unconditionally:
if (!has_acpi_companion(uart->port.dev)) {
has_acpi_companion() reads dev->fwnode without a NULL guard
(include/linux/acpi.h), so this NULL-derefs the kernel for the
remaining no-dev case rather than just skipping the
mctrl_gpio_init() initialisation as intended.
smatch flags the inconsistency:
drivers/tty/serial/8250/8250_core.c:767
serial8250_register_8250_port() error: 'uart->port.dev' could be
null (see line 719)
Guard the call with a NULL check so register continues to work
for callers that legitimately have no parent device (legacy
non-OF/non-ACPI registrations).
No functional change for callers that pass a non-NULL ->dev.
Signed-off-by: Stepan Ionichev <sozdayvek@gmail.com>
---
drivers/tty/serial/8250/8250_core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index a428e8893..e136cec0c 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -764,7 +764,7 @@ int serial8250_register_8250_port(const struct uart_8250_port *up)
* Only call mctrl_gpio_init(), if the device has no ACPI
* companion device
*/
- if (!has_acpi_companion(uart->port.dev)) {
+ if (uart->port.dev && !has_acpi_companion(uart->port.dev)) {
struct mctrl_gpios *gpios = mctrl_gpio_init(&uart->port, 0);
if (IS_ERR(gpios)) {
ret = PTR_ERR(gpios);
--
2.43.0
reply other threads:[~2026-05-08 19:13 UTC|newest]
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