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__module_address() can be invoked within a RCU section, there is no requirement to have preemption disabled. The _notrace() variant was introduced in commit14c4c8e415("cfi: Use rcu_read_{un}lock_sched_notrace"). The recursive case where __cfi_slowpath_diag() could end up calling itself is no longer present, as all that logic is gone since commit8924560094("cfi: Switch to -fsanitize=kcfi"). Sami Tolvanen said that KCFI checks don't perform function calls. Elliot Berman verified it with | modprobe -a dummy_stm stm_ftrace stm_p_basic | mkdir -p /sys/kernel/config/stp-policy/dummy_stm.0.my-policy/default | echo function > /sys/kernel/tracing/current_tracer | echo 1 > /sys/kernel/tracing/tracing_on | echo dummy_stm.0 > /sys/class/stm_source/ftrace/stm_source_link Replace the rcu_read_lock_sched_notrace() section around __module_address() with RCU. Cc: Elliot Berman <quic_eberman@quicinc.com> Cc: Kees Cook <kees@kernel.org> Cc: Nathan Chancellor <nathan@kernel.org> Cc: Sami Tolvanen <samitolvanen@google.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: llvm@lists.linux.dev Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Elliot Berman <elliot.berman@oss.qualcomm.com> # sm8650-qrd [1] Link: https://lore.kernel.org/all/20241230185812429-0800.eberman@hu-eberman-lv.qualcomm.com [1] Link: https://lore.kernel.org/r/20250108090457.512198-22-bigeasy@linutronix.de Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
99 lines
2.1 KiB
C
99 lines
2.1 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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guard(rcu)();
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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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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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