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/x86/boot/cpu.c | 86 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 86 insertions(+) create mode 100644 arch/x86/boot/cpu.c (limited to 'arch/x86/boot/cpu.c') diff --git a/arch/x86/boot/cpu.c b/arch/x86/boot/cpu.c new file mode 100644 index 000000000..feb6dbd7c --- /dev/null +++ b/arch/x86/boot/cpu.c @@ -0,0 +1,86 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* -*- linux-c -*- ------------------------------------------------------- * + * + * Copyright (C) 1991, 1992 Linus Torvalds + * Copyright 2007-2008 rPath, Inc. - All Rights Reserved + * + * ----------------------------------------------------------------------- */ + +/* + * arch/x86/boot/cpu.c + * + * Check for obligatory CPU features and abort if the features are not + * present. + */ + +#include "boot.h" +#include "cpustr.h" + +static char *cpu_name(int level) +{ + static char buf[6]; + + if (level == 64) { + return "x86-64"; + } else { + if (level == 15) + level = 6; + sprintf(buf, "i%d86", level); + return buf; + } +} + +static void show_cap_strs(u32 *err_flags) +{ + int i, j; + const unsigned char *msg_strs = (const unsigned char *)x86_cap_strs; + for (i = 0; i < NCAPINTS; i++) { + u32 e = err_flags[i]; + for (j = 0; j < 32; j++) { + if (msg_strs[0] < i || + (msg_strs[0] == i && msg_strs[1] < j)) { + /* Skip to the next string */ + msg_strs += 2; + while (*msg_strs++) + ; + } + if (e & 1) { + if (msg_strs[0] == i && + msg_strs[1] == j && + msg_strs[2]) + printf("%s ", msg_strs+2); + else + printf("%d:%d ", i, j); + } + e >>= 1; + } + } +} + +int validate_cpu(void) +{ + u32 *err_flags; + int cpu_level, req_level; + + check_cpu(&cpu_level, &req_level, &err_flags); + + if (cpu_level < req_level) { + printf("This kernel requires an %s CPU, ", + cpu_name(req_level)); + printf("but only detected an %s CPU.\n", + cpu_name(cpu_level)); + return -1; + } + + if (err_flags) { + puts("This kernel requires the following features " + "not present on the CPU:\n"); + show_cap_strs(err_flags); + putchar('\n'); + return -1; + } else if (check_knl_erratum()) { + return -1; + } else { + return 0; + } +} -- cgit v1.3.1