| // Copyright 2021 The Chromium Authors |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include"base/stack_canary_linux.h" |
| |
| #include<dlfcn.h> |
| #include<stdint.h> |
| #include<sys/mman.h> |
| |
| #include"base/bits.h" |
| #include"base/check_op.h" |
| #include"base/compiler_specific.h" |
| #include"base/logging.h" |
| #include"base/memory/page_size.h" |
| #include"base/rand_util.h" |
| #include"build/build_config.h" |
| |
| namespace base{ |
| |
| #if defined(LIBC_GLIBC) |
| |
| #if defined(ARCH_CPU_ARM_FAMILY) |
| // On ARM, Glibc uses a global variable (exported) called __stack_chk_guard. |
| extern"C"{ |
| externuintptr_t __stack_chk_guard; |
| } |
| #endif// defined(ARCH_CPU_ARM_FAMILY) |
| |
| #if !defined(NDEBUG) |
| // In debug builds, if we detect stack smashing in old stack frames after |
| // changing the canary, it's nice to let someone know that it's because the |
| // canary changed and they should prevent their function from using stack |
| // canaries. |
| staticbool g_emit_debug_message=false; |
| |
| extern"C"{ |
| typedef __attribute__((noreturn))void(GLibcStackChkFailFunction)(); |
| |
| // This overrides glibc's version of __stack_chk_fail(), which is called when |
| // the canary doesn't match. |
| __attribute__((visibility("default"), noinline, noreturn))void |
| __stack_chk_fail(){ |
| if(g_emit_debug_message){ |
| RAW_LOG( |
| FATAL, |
| "Stack smashing detected. The canary was changed during runtime " |
| "(see crbug.com/1206626). You may need to mark your function with " |
| "the no_stack_protector attribute, or just exit() before stack " |
| "smashing occurs. You can also disable this canary-changing feature " |
| "by adding --change-stack-guard-on-fork=disable to the command line."); |
| } |
| |
| // Call the real __stack_chk_fail(). |
| // Note that dlsym may not be safe to perform since this is called during |
| // corruption, but this code purposely only runs in debug builds and in the |
| // normal case might provide better debug information. |
| GLibcStackChkFailFunction* glibc_stack_chk_fail= |
| reinterpret_cast<GLibcStackChkFailFunction*>( |
| dlsym(RTLD_NEXT,"__stack_chk_fail")); |
| (*glibc_stack_chk_fail)(); |
| } |
| } |
| #endif// !defined(NDEBUG) |
| |
| NO_STACK_PROTECTORvoidResetStackCanaryIfPossible(){ |
| uintptr_t canary; |
| base::RandBytes(base::byte_span_from_ref(canary)); |
| // First byte should be the null byte for string functions. |
| canary&=~static_cast<uintptr_t>(0xff); |
| |
| // The x86/x64 offsets should work for musl too. |
| #if defined(ARCH_CPU_X86_64) |
| asmvolatile("movq %q0,%%fs:%P1"::"er"(canary),"i"(0x28)); |
| #elif defined(ARCH_CPU_X86) |
| asmvolatile("movl %0,%%gs:%P1"::"ir"(canary),"i"(0x14)); |
| #elif defined(ARCH_CPU_ARM_FAMILY) |
| // ARM's stack canary is held on a relro page. So, we'll need to make the page |
| // writable, change the stack canary, and then make the page ro again. |
| // We want to be single-threaded when changing page permissions, since it's |
| // reasonable for other threads to assume that page permissions for global |
| // variables don't change. |
| size_t page_size= base::GetPageSize(); |
| uintptr_t __stack_chk_guard_page= base::bits::AlignDown( |
| reinterpret_cast<uintptr_t>(&__stack_chk_guard), page_size); |
| PCHECK(0== mprotect(reinterpret_cast<void*>(__stack_chk_guard_page), |
| page_size, PROT_READ| PROT_WRITE)); |
| __stack_chk_guard= canary; |
| PCHECK(0== mprotect(reinterpret_cast<void*>(__stack_chk_guard_page), |
| page_size, PROT_READ)); |
| #endif |
| } |
| |
| voidSetStackSmashingEmitsDebugMessage(){ |
| #if !defined(NDEBUG) |
| g_emit_debug_message=true; |
| #endif// !defined(NDEBUG) |
| } |
| |
| #else// defined(LIBC_GLIBC) |
| |
| // We don't know how to reset the canary if not compiling for glibc. |
| voidResetStackCanaryIfPossible(){} |
| |
| voidSetStackSmashingEmitsDebugMessage(){} |
| |
| #endif// defined(LIBC_GLIBC) |
| }// namespace base |
