From 78004e9a87f240df03e2f73120d291763c32e0a7 Mon Sep 17 00:00:00 2001 From: Ali Ahmet Memis Date: Fri, 21 Aug 2026 01:45:27 +0000 Subject: openrisc: fix arbitrary kernel memory access via or1k_atomic syscall sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user pointers, v1 and v2, and swaps the words they point to in hand-written assembly. l.lwz r29,0(r4) l.lwz r27,0(r5) l.sw 0(r4),r27 l.sw 0(r5),r29 The pointers are not checked with access_ok(). The four memory accesses also have no exception table entries. A caller passes a kernel address as either pointer, and the syscall reads from and writes to it directly. This gives an unprivileged process a kernel read/write primitive. It overwrites kernel data such as the sys_call_table, gaining code execution in kernel context. Check both pointers before entering the critical section. Add fixups for the four memory accesses so faults on valid but unmapped user addresses return -EFAULT. [shorne@gmail.com: fix comment style] Fixes: 9d02a4283e9c ("OpenRISC: Boot code") Cc: stable@vger.kernel.org Signed-off-by: Ali Ahmet Memis Signed-off-by: Stafford Horne --- drivers/misc/ibmasm/uart.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 58 insertions(+) create mode 100644 drivers/misc/ibmasm/uart.c (limited to 'drivers/misc/ibmasm/uart.c') diff --git a/drivers/misc/ibmasm/uart.c b/drivers/misc/ibmasm/uart.c new file mode 100644 index 000000000..a5d4c8e01 --- /dev/null +++ b/drivers/misc/ibmasm/uart.c @@ -0,0 +1,58 @@ +// SPDX-License-Identifier: GPL-2.0-or-later + +/* + * IBM ASM Service Processor Device Driver + * + * Copyright (C) IBM Corporation, 2004 + * + * Author: Max Asböck + */ + +#include +#include +#include +#include +#include +#include "ibmasm.h" +#include "lowlevel.h" + + +void ibmasm_register_uart(struct service_processor *sp) +{ + struct uart_8250_port uart; + void __iomem *iomem_base; + + iomem_base = sp->base_address + SCOUT_COM_B_BASE; + + /* read the uart scratch register to determine if the UART + * is dedicated to the service processor or if the OS can use it + */ + if (0 == readl(iomem_base + UART_SCR)) { + dev_info(sp->dev, "IBM SP UART not registered, owned by service processor\n"); + sp->serial_line = -1; + return; + } + + memset(&uart, 0, sizeof(uart)); + uart.port.irq = sp->irq; + uart.port.uartclk = 3686400; + uart.port.flags = UPF_SHARE_IRQ; + uart.port.iotype = UPIO_MEM; + uart.port.membase = iomem_base; + + sp->serial_line = serial8250_register_8250_port(&uart); + if (sp->serial_line < 0) { + dev_err(sp->dev, "Failed to register serial port\n"); + return; + } + enable_uart_interrupts(sp->base_address); +} + +void ibmasm_unregister_uart(struct service_processor *sp) +{ + if (sp->serial_line < 0) + return; + + disable_uart_interrupts(sp->base_address); + serial8250_unregister_port(sp->serial_line); +} -- cgit v1.3.1