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/*
* Copyright (C) 2019 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "heap_tagging.h"
#include "malloc_common.h"
#include "malloc_tagged_pointers.h"
#include <bionic/pthread_internal.h>
#include <platform/bionic/malloc.h>
#include <sanitizer/hwasan_interface.h>
#include <sys/auxv.h>
extern "C" void scudo_malloc_disable_memory_tagging();
extern "C" void scudo_malloc_set_track_allocation_stacks(int);
// Protected by `g_heap_tagging_lock`.
static HeapTaggingLevel heap_tagging_level = M_HEAP_TAGGING_LEVEL_NONE;
void SetDefaultHeapTaggingLevel() {
#if defined(__aarch64__)
#if !__has_feature(hwaddress_sanitizer)
heap_tagging_level = __libc_shared_globals()->initial_heap_tagging_level;
#endif
__libc_globals.mutate([](libc_globals* globals) {
switch (heap_tagging_level) {
case M_HEAP_TAGGING_LEVEL_TBI:
// Arrange for us to set pointer tags to POINTER_TAG, check tags on
// deallocation and untag when passing pointers to the allocator.
globals->heap_pointer_tag = (reinterpret_cast<uintptr_t>(POINTER_TAG) << TAG_SHIFT) |
(0xffull << CHECK_SHIFT) | (0xffull << UNTAG_SHIFT);
break;
case M_HEAP_TAGGING_LEVEL_SYNC:
case M_HEAP_TAGGING_LEVEL_ASYNC:
atomic_store(&globals->memtag, true);
atomic_store(&__libc_memtag_stack, __libc_shared_globals()->initial_memtag_stack);
break;
default:
break;
};
});
#if defined(USE_SCUDO) && !__has_feature(hwaddress_sanitizer)
switch (heap_tagging_level) {
case M_HEAP_TAGGING_LEVEL_TBI:
case M_HEAP_TAGGING_LEVEL_NONE:
scudo_malloc_disable_memory_tagging();
break;
case M_HEAP_TAGGING_LEVEL_SYNC:
scudo_malloc_set_track_allocation_stacks(1);
break;
default:
break;
}
#endif // USE_SCUDO
#endif // aarch64
}
static bool set_tcf_on_all_threads(int tcf) {
return android_run_on_all_threads(
[](void* arg) {
int tcf = *reinterpret_cast<int*>(arg);
int tagged_addr_ctrl = prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0);
if (tagged_addr_ctrl < 0) {
return false;
}
tagged_addr_ctrl = (tagged_addr_ctrl & ~PR_MTE_TCF_MASK) | tcf;
return prctl(PR_SET_TAGGED_ADDR_CTRL, tagged_addr_ctrl, 0, 0, 0) >= 0;
},
&tcf);
}
pthread_mutex_t g_heap_tagging_lock = PTHREAD_MUTEX_INITIALIZER;
// Requires `g_heap_tagging_lock` to be held.
bool SetHeapTaggingLevel(HeapTaggingLevel tag_level) {
if (tag_level == heap_tagging_level) {
return true;
}
switch (tag_level) {
case M_HEAP_TAGGING_LEVEL_NONE:
__libc_globals.mutate([](libc_globals* globals) {
if (heap_tagging_level == M_HEAP_TAGGING_LEVEL_TBI) {
// Preserve the untag mask (we still want to untag pointers when passing them to the
// allocator), but clear the fixed tag and the check mask, so that pointers are no longer
// tagged and checks no longer happen.
globals->heap_pointer_tag = static_cast<uintptr_t>(0xffull << UNTAG_SHIFT);
}
atomic_store(&__libc_memtag_stack, false);
atomic_store(&globals->memtag, false);
});
if (heap_tagging_level != M_HEAP_TAGGING_LEVEL_TBI) {
if (!set_tcf_on_all_threads(PR_MTE_TCF_NONE)) {
error_log("SetHeapTaggingLevel: set_tcf_on_all_threads failed");
return false;
}
}
#if defined(USE_SCUDO) && !__has_feature(hwaddress_sanitizer)
scudo_malloc_disable_memory_tagging();
#endif
break;
case M_HEAP_TAGGING_LEVEL_TBI:
case M_HEAP_TAGGING_LEVEL_ASYNC:
case M_HEAP_TAGGING_LEVEL_SYNC:
if (heap_tagging_level == M_HEAP_TAGGING_LEVEL_NONE) {
#if !__has_feature(hwaddress_sanitizer)
// Suppress the error message in HWASan builds. Apps can try to enable TBI (or even MTE
// modes) being unaware of HWASan, fail them silently.
error_log(
"SetHeapTaggingLevel: re-enabling tagging after it was disabled is not supported");
#endif
return false;
} else if (tag_level == M_HEAP_TAGGING_LEVEL_TBI ||
heap_tagging_level == M_HEAP_TAGGING_LEVEL_TBI) {
error_log("SetHeapTaggingLevel: switching between TBI and ASYNC/SYNC is not supported");
return false;
}
if (tag_level == M_HEAP_TAGGING_LEVEL_ASYNC) {
// When entering ASYNC mode, specify that we want to allow upgrading to SYNC by OR'ing in
// the SYNC flag. But if the kernel doesn't support specifying multiple TCF modes, fall back
// to specifying a single mode.
if (!set_tcf_on_all_threads(PR_MTE_TCF_ASYNC | PR_MTE_TCF_SYNC)) {
set_tcf_on_all_threads(PR_MTE_TCF_ASYNC);
}
#if defined(USE_SCUDO) && !__has_feature(hwaddress_sanitizer)
scudo_malloc_set_track_allocation_stacks(0);
#endif
} else if (tag_level == M_HEAP_TAGGING_LEVEL_SYNC) {
set_tcf_on_all_threads(PR_MTE_TCF_SYNC);
#if defined(USE_SCUDO) && !__has_feature(hwaddress_sanitizer)
scudo_malloc_set_track_allocation_stacks(1);
#endif
}
break;
default:
error_log("SetHeapTaggingLevel: unknown tagging level");
return false;
}
heap_tagging_level = tag_level;
info_log("SetHeapTaggingLevel: tag level set to %d", tag_level);
return true;
}
#ifdef __aarch64__
static inline __attribute__((no_sanitize("memtag"))) void untag_memory(void* from, void* to) {
__asm__ __volatile__(
".arch_extension mte\n"
"1:\n"
"stg %[Ptr], [%[Ptr]], #16\n"
"cmp %[Ptr], %[End]\n"
"b.lt 1b\n"
: [Ptr] "+&r"(from)
: [End] "r"(to)
: "memory");
}
#endif
#ifdef __aarch64__
// 128Mb of stack should be enough for anybody.
static constexpr size_t kUntagLimit = 128 * 1024 * 1024;
#endif // __aarch64__
extern "C" __LIBC_HIDDEN__ __attribute__((no_sanitize("memtag"))) void memtag_handle_longjmp(
void* sp_dst __unused, void* sp_src __unused) {
// A usual longjmp looks like this, where sp_dst was the LR in the call to setlongjmp (i.e.
// the SP of the frame calling setlongjmp).
// ┌─────────────────────┐ │
// │ │ │
// ├─────────────────────┤◄──────── sp_dst │ stack
// │ ... │ │ grows
// ├─────────────────────┤ │ to lower
// │ ... │ │ addresses
// ├─────────────────────┤◄──────── sp_src │
// │siglongjmp │ │
// ├─────────────────────┤ │
// │memtag_handle_longjmp│ │
// └─────────────────────┘ ▼
#ifdef __aarch64__
if (atomic_load(&__libc_memtag_stack)) {
size_t distance = reinterpret_cast<uintptr_t>(sp_dst) - reinterpret_cast<uintptr_t>(sp_src);
if (distance > kUntagLimit) {
async_safe_fatal(
"memtag_handle_longjmp: stack adjustment too large! %p -> %p, distance %zx > %zx\n",
sp_src, sp_dst, distance, kUntagLimit);
} else {
untag_memory(sp_src, sp_dst);
}
}
#endif // __aarch64__
// We can use __has_feature here rather than __hwasan_handle_longjmp as a
// weak symbol because this is part of libc which is always sanitized for a
// hwasan enabled process.
#if __has_feature(hwaddress_sanitizer)
__hwasan_handle_longjmp(sp_dst);
#endif // __has_feature(hwaddress_sanitizer)
}
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