CVE-2026-97480tty: serial: 8250: protect against NULL uart->port.dev in register

Official description

In the Linux kernel, the following vulnerability has been resolved: tty: serial: 8250: protect against NULL uart->port.dev in register 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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/f728f7f38a6eca16923c72fc6826445810d2b41f
• https://git.kernel.org/stable/c/68059b6e9f7292714286e2b0f5185ed2a43fccc5
• https://git.kernel.org/stable/c/9c78f89cf2fbae18b14c78bf172ca15d832aff15
• https://git.kernel.org/stable/c/5cbab666721d974bfe033a12045d808936deaefd
• https://git.kernel.org/stable/c/941c9f84c9b6310f7aaa1c8c785dcc634ee33050