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8924560094
Switch from Clang's original forward-edge control-flow integrity implementation to -fsanitize=kcfi, which is better suited for the kernel, as it doesn't require LTO, doesn't use a jump table that requires altering function references, and won't break cross-module function address equality. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Tested-by: Kees Cook <keescook@chromium.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20220908215504.3686827-6-samitolvanen@google.com
101 lines
2.2 KiB
C
101 lines
2.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Clang Control Flow Integrity (CFI) error handling.
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*
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* Copyright (C) 2022 Google LLC
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*/
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#include <linux/cfi.h>
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enum bug_trap_type report_cfi_failure(struct pt_regs *regs, unsigned long addr,
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unsigned long *target, u32 type)
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{
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if (target)
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pr_err("CFI failure at %pS (target: %pS; expected type: 0x%08x)\n",
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(void *)addr, (void *)*target, type);
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else
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pr_err("CFI failure at %pS (no target information)\n",
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(void *)addr);
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if (IS_ENABLED(CONFIG_CFI_PERMISSIVE)) {
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__warn(NULL, 0, (void *)addr, 0, regs, NULL);
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return BUG_TRAP_TYPE_WARN;
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}
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return BUG_TRAP_TYPE_BUG;
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}
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#ifdef CONFIG_ARCH_USES_CFI_TRAPS
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static inline unsigned long trap_address(s32 *p)
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{
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return (unsigned long)((long)p + (long)*p);
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}
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static bool is_trap(unsigned long addr, s32 *start, s32 *end)
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{
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s32 *p;
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for (p = start; p < end; ++p) {
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if (trap_address(p) == addr)
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return true;
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}
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return false;
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}
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#ifdef CONFIG_MODULES
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/* Populates `kcfi_trap(_end)?` fields in `struct module`. */
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void module_cfi_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
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struct module *mod)
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{
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char *secstrings;
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unsigned int i;
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mod->kcfi_traps = NULL;
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mod->kcfi_traps_end = NULL;
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secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
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for (i = 1; i < hdr->e_shnum; i++) {
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if (strcmp(secstrings + sechdrs[i].sh_name, "__kcfi_traps"))
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continue;
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mod->kcfi_traps = (s32 *)sechdrs[i].sh_addr;
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mod->kcfi_traps_end = (s32 *)(sechdrs[i].sh_addr + sechdrs[i].sh_size);
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break;
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}
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}
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static bool is_module_cfi_trap(unsigned long addr)
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{
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struct module *mod;
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bool found = false;
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rcu_read_lock_sched_notrace();
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mod = __module_address(addr);
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if (mod)
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found = is_trap(addr, mod->kcfi_traps, mod->kcfi_traps_end);
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rcu_read_unlock_sched_notrace();
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return found;
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}
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#else /* CONFIG_MODULES */
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static inline bool is_module_cfi_trap(unsigned long addr)
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{
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return false;
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}
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#endif /* CONFIG_MODULES */
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extern s32 __start___kcfi_traps[];
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extern s32 __stop___kcfi_traps[];
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bool is_cfi_trap(unsigned long addr)
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{
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if (is_trap(addr, __start___kcfi_traps, __stop___kcfi_traps))
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return true;
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return is_module_cfi_trap(addr);
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}
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#endif /* CONFIG_ARCH_USES_CFI_TRAPS */
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