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Merge "Add libfstab_fuzzer that fuzzes ReadFstabFile()"

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Treehugger Robot 2021-10-26 07:50:24 +00:00 committed by Gerrit Code Review
commit 6aa256fdf6
4 changed files with 138 additions and 77 deletions
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154
fs_mgr/fs_mgr_fstab.cpp
View file

@ -442,7 +442,81 @@ std::string GetFstabPath() {
return "";
}
bool ReadFstabFile(FILE* fstab_file, bool proc_mounts, Fstab* fstab_out) {
/* Extracts <device>s from the by-name symlinks specified in a fstab:
* /dev/block/<type>/<device>/by-name/<partition>
*
* <type> can be: platform, pci or vbd.
*
* For example, given the following entries in the input fstab:
* /dev/block/platform/soc/1da4000.ufshc/by-name/system
* /dev/block/pci/soc.0/f9824900.sdhci/by-name/vendor
* it returns a set { "soc/1da4000.ufshc", "soc.0/f9824900.sdhci" }.
*/
std::set<std::string> ExtraBootDevices(const Fstab& fstab) {
std::set<std::string> boot_devices;
for (const auto& entry : fstab) {
std::string blk_device = entry.blk_device;
// Skips blk_device that doesn't conform to the format.
if (!android::base::StartsWith(blk_device, "/dev/block") ||
android::base::StartsWith(blk_device, "/dev/block/by-name") ||
android::base::StartsWith(blk_device, "/dev/block/bootdevice/by-name")) {
continue;
}
// Skips non-by_name blk_device.
// /dev/block/<type>/<device>/by-name/<partition>
// ^ slash_by_name
auto slash_by_name = blk_device.find("/by-name");
if (slash_by_name == std::string::npos) continue;
blk_device.erase(slash_by_name); // erases /by-name/<partition>
// Erases /dev/block/, now we have <type>/<device>
blk_device.erase(0, std::string("/dev/block/").size());
// <type>/<device>
// ^ first_slash
auto first_slash = blk_device.find('/');
if (first_slash == std::string::npos) continue;
auto boot_device = blk_device.substr(first_slash + 1);
if (!boot_device.empty()) boot_devices.insert(std::move(boot_device));
}
return boot_devices;
}
FstabEntry BuildDsuUserdataFstabEntry() {
constexpr uint32_t kFlags = MS_NOATIME | MS_NOSUID | MS_NODEV;
FstabEntry userdata = {
.blk_device = "userdata_gsi",
.mount_point = "/data",
.fs_type = "ext4",
.flags = kFlags,
.reserved_size = 128 * 1024 * 1024,
};
userdata.fs_mgr_flags.wait = true;
userdata.fs_mgr_flags.check = true;
userdata.fs_mgr_flags.logical = true;
userdata.fs_mgr_flags.quota = true;
userdata.fs_mgr_flags.late_mount = true;
userdata.fs_mgr_flags.formattable = true;
return userdata;
}
bool EraseFstabEntry(Fstab* fstab, const std::string& mount_point) {
auto iter = std::remove_if(fstab->begin(), fstab->end(),
[&](const auto& entry) { return entry.mount_point == mount_point; });
if (iter != fstab->end()) {
fstab->erase(iter, fstab->end());
return true;
}
return false;
}
} // namespace
bool ReadFstabFromFp(FILE* fstab_file, bool proc_mounts, Fstab* fstab_out) {
ssize_t len;
size_t alloc_len = 0;
char *line = NULL;
@ -528,80 +602,6 @@ err:
return false;
}
/* Extracts <device>s from the by-name symlinks specified in a fstab:
* /dev/block/<type>/<device>/by-name/<partition>
*
* <type> can be: platform, pci or vbd.
*
* For example, given the following entries in the input fstab:
* /dev/block/platform/soc/1da4000.ufshc/by-name/system
* /dev/block/pci/soc.0/f9824900.sdhci/by-name/vendor
* it returns a set { "soc/1da4000.ufshc", "soc.0/f9824900.sdhci" }.
*/
std::set<std::string> ExtraBootDevices(const Fstab& fstab) {
std::set<std::string> boot_devices;
for (const auto& entry : fstab) {
std::string blk_device = entry.blk_device;
// Skips blk_device that doesn't conform to the format.
if (!android::base::StartsWith(blk_device, "/dev/block") ||
android::base::StartsWith(blk_device, "/dev/block/by-name") ||
android::base::StartsWith(blk_device, "/dev/block/bootdevice/by-name")) {
continue;
}
// Skips non-by_name blk_device.
// /dev/block/<type>/<device>/by-name/<partition>
// ^ slash_by_name
auto slash_by_name = blk_device.find("/by-name");
if (slash_by_name == std::string::npos) continue;
blk_device.erase(slash_by_name); // erases /by-name/<partition>
// Erases /dev/block/, now we have <type>/<device>
blk_device.erase(0, std::string("/dev/block/").size());
// <type>/<device>
// ^ first_slash
auto first_slash = blk_device.find('/');
if (first_slash == std::string::npos) continue;
auto boot_device = blk_device.substr(first_slash + 1);
if (!boot_device.empty()) boot_devices.insert(std::move(boot_device));
}
return boot_devices;
}
FstabEntry BuildDsuUserdataFstabEntry() {
constexpr uint32_t kFlags = MS_NOATIME | MS_NOSUID | MS_NODEV;
FstabEntry userdata = {
.blk_device = "userdata_gsi",
.mount_point = "/data",
.fs_type = "ext4",
.flags = kFlags,
.reserved_size = 128 * 1024 * 1024,
};
userdata.fs_mgr_flags.wait = true;
userdata.fs_mgr_flags.check = true;
userdata.fs_mgr_flags.logical = true;
userdata.fs_mgr_flags.quota = true;
userdata.fs_mgr_flags.late_mount = true;
userdata.fs_mgr_flags.formattable = true;
return userdata;
}
bool EraseFstabEntry(Fstab* fstab, const std::string& mount_point) {
auto iter = std::remove_if(fstab->begin(), fstab->end(),
[&](const auto& entry) { return entry.mount_point == mount_point; });
if (iter != fstab->end()) {
fstab->erase(iter, fstab->end());
return true;
}
return false;
}
} // namespace
void TransformFstabForDsu(Fstab* fstab, const std::string& dsu_slot,
const std::vector<std::string>& dsu_partitions) {
static constexpr char kDsuKeysDir[] = "/avb";
@ -707,7 +707,7 @@ bool ReadFstabFromFile(const std::string& path, Fstab* fstab_out) {
bool is_proc_mounts = path == "/proc/mounts";
Fstab fstab;
if (!ReadFstabFile(fstab_file.get(), is_proc_mounts, &fstab)) {
if (!ReadFstabFromFp(fstab_file.get(), is_proc_mounts, &fstab)) {
LERROR << __FUNCTION__ << "(): failed to load fstab from : '" << path << "'";
return false;
}
@ -762,7 +762,7 @@ bool ReadFstabFromDt(Fstab* fstab, bool verbose) {
return false;
}
if (!ReadFstabFile(fstab_file.get(), false, fstab)) {
if (!ReadFstabFromFp(fstab_file.get(), false, fstab)) {
if (verbose) {
LERROR << __FUNCTION__ << "(): failed to load fstab from kernel:" << std::endl
<< fstab_buf;

28
fs_mgr/fuzz/Android.bp Normal file
View file

@ -0,0 +1,28 @@
//
// Copyright (C) 2021 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
cc_fuzz {
name: "libfstab_fuzzer",
srcs: [
"fs_mgr_fstab_fuzzer.cpp",
],
static_libs: [
"libfstab",
],
shared_libs: [
"libbase",
],
}

30
fs_mgr/fuzz/fs_mgr_fstab_fuzzer.cpp Normal file
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@ -0,0 +1,30 @@
//
// Copyright (C) 2021 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#include <cstdio>
#include <fstab/fstab.h>
extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
std::unique_ptr<FILE, decltype(&fclose)> fstab_file(
fmemopen(static_cast<void*>(const_cast<uint8_t*>(data)), size, "r"), fclose);
if (fstab_file == nullptr) {
return 0;
}
android::fs_mgr::Fstab fstab;
android::fs_mgr::ReadFstabFromFp(fstab_file.get(), /* proc_mounts= */ false, &fstab);
return 0;
}

3
fs_mgr/include_fstab/fstab/fstab.h
View file

@ -99,6 +99,9 @@ struct FstabEntry {
// Unless explicitly requested, a lookup on mount point should always return the 1st one.
using Fstab = std::vector<FstabEntry>;
// Exported for testability. Regular users should use ReadFstabFromfile().
bool ReadFstabFromFp(FILE* fstab_file, bool proc_mounts, Fstab* fstab_out);
bool ReadFstabFromFile(const std::string& path, Fstab* fstab);
bool ReadFstabFromDt(Fstab* fstab, bool verbose = true);
bool ReadDefaultFstab(Fstab* fstab);