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/acpi/bgrt.c | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 94 insertions(+) create mode 100644 drivers/acpi/bgrt.c (limited to 'drivers/acpi/bgrt.c') diff --git a/drivers/acpi/bgrt.c b/drivers/acpi/bgrt.c new file mode 100644 index 000000000..0fdd581ef --- /dev/null +++ b/drivers/acpi/bgrt.c @@ -0,0 +1,94 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * BGRT boot graphic support + * Authors: Matthew Garrett, Josh Triplett + * Copyright 2012 Red Hat, Inc + * Copyright 2012 Intel Corporation + */ + +#include +#include +#include +#include +#include + +static void *bgrt_image; +static struct kobject *bgrt_kobj; + +#define BGRT_SHOW(_name, _member) \ + static ssize_t _name##_show(struct kobject *kobj, \ + struct kobj_attribute *attr, char *buf) \ + { \ + return sysfs_emit(buf, "%d\n", bgrt_tab._member); \ + } \ + static struct kobj_attribute bgrt_attr_##_name = __ATTR_RO(_name) + +BGRT_SHOW(version, version); +BGRT_SHOW(status, status); +BGRT_SHOW(type, image_type); +BGRT_SHOW(xoffset, image_offset_x); +BGRT_SHOW(yoffset, image_offset_y); + +static __ro_after_init BIN_ATTR_SIMPLE_RO(image); + +static struct attribute *bgrt_attributes[] = { + &bgrt_attr_version.attr, + &bgrt_attr_status.attr, + &bgrt_attr_type.attr, + &bgrt_attr_xoffset.attr, + &bgrt_attr_yoffset.attr, + NULL, +}; + +static const struct bin_attribute *const bgrt_bin_attributes[] = { + &bin_attr_image, + NULL, +}; + +static const struct attribute_group bgrt_attribute_group = { + .attrs = bgrt_attributes, + .bin_attrs = bgrt_bin_attributes, +}; + +int __init acpi_parse_bgrt(struct acpi_table_header *table) +{ + efi_bgrt_init(table); + return 0; +} + +static int __init bgrt_init(void) +{ + int ret; + + if (!bgrt_tab.image_address) + return -ENODEV; + + bgrt_image = memremap(bgrt_tab.image_address, bgrt_image_size, + MEMREMAP_WB); + if (!bgrt_image) { + pr_notice("Ignoring BGRT: failed to map image memory\n"); + return -ENOMEM; + } + + bin_attr_image.private = bgrt_image; + bin_attr_image.size = bgrt_image_size; + + bgrt_kobj = kobject_create_and_add("bgrt", acpi_kobj); + if (!bgrt_kobj) { + ret = -EINVAL; + goto out_memmap; + } + + ret = sysfs_create_group(bgrt_kobj, &bgrt_attribute_group); + if (ret) + goto out_kobject; + + return 0; + +out_kobject: + kobject_put(bgrt_kobj); +out_memmap: + memunmap(bgrt_image); + return ret; +} +device_initcall(bgrt_init); -- cgit v1.3.1