| Avi Drissman | e4622aa | 2022-09-08 20:36:06 | [diff] [blame] | 1 | // Copyright 2021 The Chromium Authors |
| Matthew Denton | bb0b03e | 2021-07-22 16:18:13 | [diff] [blame] | 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #include"base/stack_canary_linux.h" |
| 6 | |
| 7 | #include<dlfcn.h> |
| 8 | #include<stdint.h> |
| 9 | #include<sys/mman.h> |
| 10 | |
| 11 | #include"base/bits.h" |
| 12 | #include"base/check_op.h" |
| 13 | #include"base/compiler_specific.h" |
| 14 | #include"base/logging.h" |
| 15 | #include"base/memory/page_size.h" |
| 16 | #include"base/rand_util.h" |
| 17 | #include"build/build_config.h" |
| 18 | |
| 19 | namespace base{ |
| 20 | |
| 21 | #if defined(LIBC_GLIBC) |
| 22 | |
| 23 | #if defined(ARCH_CPU_ARM_FAMILY) |
| 24 | // On ARM, Glibc uses a global variable (exported) called __stack_chk_guard. |
| 25 | extern"C"{ |
| 26 | externuintptr_t __stack_chk_guard; |
| 27 | } |
| 28 | #endif// defined(ARCH_CPU_ARM_FAMILY) |
| 29 | |
| 30 | #if !defined(NDEBUG) |
| 31 | // In debug builds, if we detect stack smashing in old stack frames after |
| 32 | // changing the canary, it's nice to let someone know that it's because the |
| 33 | // canary changed and they should prevent their function from using stack |
| 34 | // canaries. |
| 35 | staticbool g_emit_debug_message=false; |
| 36 | |
| 37 | extern"C"{ |
| 38 | typedef __attribute__((noreturn))void(GLibcStackChkFailFunction)(); |
| 39 | |
| 40 | // This overrides glibc's version of __stack_chk_fail(), which is called when |
| 41 | // the canary doesn't match. |
| 42 | __attribute__((visibility("default"), noinline, noreturn))void |
| 43 | __stack_chk_fail(){ |
| 44 | if(g_emit_debug_message){ |
| 45 | RAW_LOG( |
| 46 | FATAL, |
| 47 | "Stack smashing detected. The canary was changed during runtime " |
| 48 | "(see crbug.com/1206626). You may need to mark your function with " |
| 49 | "the no_stack_protector attribute, or just exit() before stack " |
| 50 | "smashing occurs. You can also disable this canary-changing feature " |
| 51 | "by adding --change-stack-guard-on-fork=disable to the command line."); |
| 52 | } |
| 53 | |
| 54 | // Call the real __stack_chk_fail(). |
| 55 | // Note that dlsym may not be safe to perform since this is called during |
| 56 | // corruption, but this code purposely only runs in debug builds and in the |
| 57 | // normal case might provide better debug information. |
| 58 | GLibcStackChkFailFunction* glibc_stack_chk_fail= |
| 59 | reinterpret_cast<GLibcStackChkFailFunction*>( |
| 60 | dlsym(RTLD_NEXT,"__stack_chk_fail")); |
| 61 | (*glibc_stack_chk_fail)(); |
| 62 | } |
| 63 | } |
| 64 | #endif// !defined(NDEBUG) |
| 65 | |
| Peter Kasting | 7bf5e3f9 | 2024-09-05 17:25:19 | [diff] [blame] | 66 | NO_STACK_PROTECTORvoidResetStackCanaryIfPossible(){ |
| Matthew Denton | bb0b03e | 2021-07-22 16:18:13 | [diff] [blame] | 67 | uintptr_t canary; |
| danakj | 95305d27 | 2024-05-09 20:38:44 | [diff] [blame] | 68 | base::RandBytes(base::byte_span_from_ref(canary)); |
| Matthew Denton | bb0b03e | 2021-07-22 16:18:13 | [diff] [blame] | 69 | // First byte should be the null byte for string functions. |
| 70 | canary&=~static_cast<uintptr_t>(0xff); |
| 71 | |
| 72 | // The x86/x64 offsets should work for musl too. |
| 73 | #if defined(ARCH_CPU_X86_64) |
| 74 | asmvolatile("movq %q0,%%fs:%P1"::"er"(canary),"i"(0x28)); |
| 75 | #elif defined(ARCH_CPU_X86) |
| 76 | asmvolatile("movl %0,%%gs:%P1"::"ir"(canary),"i"(0x14)); |
| 77 | #elif defined(ARCH_CPU_ARM_FAMILY) |
| 78 | // ARM's stack canary is held on a relro page. So, we'll need to make the page |
| 79 | // writable, change the stack canary, and then make the page ro again. |
| 80 | // We want to be single-threaded when changing page permissions, since it's |
| 81 | // reasonable for other threads to assume that page permissions for global |
| 82 | // variables don't change. |
| 83 | size_t page_size= base::GetPageSize(); |
| 84 | uintptr_t __stack_chk_guard_page= base::bits::AlignDown( |
| 85 | reinterpret_cast<uintptr_t>(&__stack_chk_guard), page_size); |
| 86 | PCHECK(0== mprotect(reinterpret_cast<void*>(__stack_chk_guard_page), |
| 87 | page_size, PROT_READ| PROT_WRITE)); |
| 88 | __stack_chk_guard= canary; |
| 89 | PCHECK(0== mprotect(reinterpret_cast<void*>(__stack_chk_guard_page), |
| 90 | page_size, PROT_READ)); |
| 91 | #endif |
| 92 | } |
| 93 | |
| 94 | voidSetStackSmashingEmitsDebugMessage(){ |
| 95 | #if !defined(NDEBUG) |
| 96 | g_emit_debug_message=true; |
| 97 | #endif// !defined(NDEBUG) |
| 98 | } |
| 99 | |
| 100 | #else// defined(LIBC_GLIBC) |
| 101 | |
| 102 | // We don't know how to reset the canary if not compiling for glibc. |
| 103 | voidResetStackCanaryIfPossible(){} |
| 104 | |
| 105 | voidSetStackSmashingEmitsDebugMessage(){} |
| 106 | |
| 107 | #endif// defined(LIBC_GLIBC) |
| 108 | }// namespace base |
