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/firmware/efi/efibc.c | 92 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 92 insertions(+) create mode 100644 drivers/firmware/efi/efibc.c (limited to 'drivers/firmware/efi/efibc.c') diff --git a/drivers/firmware/efi/efibc.c b/drivers/firmware/efi/efibc.c new file mode 100644 index 000000000..345a10aa7 --- /dev/null +++ b/drivers/firmware/efi/efibc.c @@ -0,0 +1,92 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * efibc: control EFI bootloaders which obey LoaderEntryOneShot var + * Copyright (c) 2013-2016, Intel Corporation. + */ + +#define pr_fmt(fmt) "efibc: " fmt + +#include +#include +#include +#include +#include + +#define MAX_DATA_LEN 512 + +static int efibc_set_variable(efi_char16_t *name, efi_char16_t *value, + unsigned long len) +{ + efi_status_t status; + + status = efi.set_variable(name, &LINUX_EFI_LOADER_ENTRY_GUID, + EFI_VARIABLE_NON_VOLATILE + | EFI_VARIABLE_BOOTSERVICE_ACCESS + | EFI_VARIABLE_RUNTIME_ACCESS, + len * sizeof(efi_char16_t), value); + + if (status != EFI_SUCCESS) { + pr_err("failed to set EFI variable: 0x%lx\n", status); + return -EIO; + } + return 0; +} + +static int efibc_reboot_notifier_call(struct notifier_block *notifier, + unsigned long event, void *data) +{ + efi_char16_t *reason = event == SYS_RESTART ? L"reboot" + : L"shutdown"; + const u8 *str = data; + efi_char16_t *wdata; + unsigned long l; + int ret; + + ret = efibc_set_variable(L"LoaderEntryRebootReason", reason, + ucs2_strlen(reason)); + if (ret || !data) + return NOTIFY_DONE; + + wdata = kmalloc_objs(efi_char16_t, MAX_DATA_LEN); + if (!wdata) + return NOTIFY_DONE; + + for (l = 0; l < MAX_DATA_LEN - 1 && str[l] != '\0'; l++) + wdata[l] = str[l]; + wdata[l] = L'\0'; + + efibc_set_variable(L"LoaderEntryOneShot", wdata, l); + + kfree(wdata); + return NOTIFY_DONE; +} + +static struct notifier_block efibc_reboot_notifier = { + .notifier_call = efibc_reboot_notifier_call, +}; + +static int __init efibc_init(void) +{ + int ret; + + if (!efi_rt_services_supported(EFI_RT_SUPPORTED_SET_VARIABLE)) + return -ENODEV; + + ret = register_reboot_notifier(&efibc_reboot_notifier); + if (ret) + pr_err("unable to register reboot notifier\n"); + + return ret; +} +module_init(efibc_init); + +static void __exit efibc_exit(void) +{ + unregister_reboot_notifier(&efibc_reboot_notifier); +} +module_exit(efibc_exit); + +MODULE_AUTHOR("Jeremy Compostella "); +MODULE_AUTHOR("Matt Gumbel