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 --- arch/powerpc/boot/ofconsole.c | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) create mode 100644 arch/powerpc/boot/ofconsole.c (limited to 'arch/powerpc/boot/ofconsole.c') diff --git a/arch/powerpc/boot/ofconsole.c b/arch/powerpc/boot/ofconsole.c new file mode 100644 index 000000000..8eb0f1c45 --- /dev/null +++ b/arch/powerpc/boot/ofconsole.c @@ -0,0 +1,43 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * OF console routines + * + * Copyright (C) Paul Mackerras 1997. + */ +#include +#include "types.h" +#include "elf.h" +#include "string.h" +#include "stdio.h" +#include "page.h" +#include "ops.h" + +#include "of.h" + +static unsigned int of_stdout_handle; + +static int of_console_open(void) +{ + void *devp; + + if (((devp = of_finddevice("/chosen")) != NULL) + && (of_getprop(devp, "stdout", &of_stdout_handle, + sizeof(of_stdout_handle)) + == sizeof(of_stdout_handle))) { + of_stdout_handle = be32_to_cpu(of_stdout_handle); + return 0; + } + + return -1; +} + +static void of_console_write(const char *buf, int len) +{ + of_call_prom("write", 3, 1, of_stdout_handle, buf, len); +} + +void of_console_init(void) +{ + console_ops.open = of_console_open; + console_ops.write = of_console_write; +} -- cgit v1.3.1