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Merge changes I12bc2ccd,I8174257c into main

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* changes:
  fs_mgr_overlayfs: Fix "/" mount propagation type after remount
  fs_mgr_overlayfs: Fix submount propagation type after remount
This commit is contained in:
Yi-Yo Chiang 2023-11-21 09:36:47 +00:00 • committed by Gerrit Code Review
commit 7f322bcaf0
1 changed files with 60 additions and 31 deletions
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91
fs_mgr/fs_mgr_overlayfs_mount.cpp
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@ -34,6 +34,7 @@
#include <android-base/file.h>
#include <android-base/macros.h>
#include <android-base/properties.h>
#include <android-base/scopeguard.h>
#include <android-base/strings.h>
#include <android-base/unique_fd.h>
#include <ext4_utils/ext4_utils.h>
@ -58,6 +59,9 @@ constexpr char kPreferCacheBackingStorageProp[] = "fs_mgr.overlayfs.prefer_cache
constexpr char kCacheMountPoint[] = "/cache";
constexpr char kPhysicalDevice[] = "/dev/block/by-name/";
// Mount tree to temporarily hold references to submounts.
constexpr char kMoveMountTempDir[] = "/dev/remount";
constexpr char kLowerdirOption[] = "lowerdir=";
constexpr char kUpperdirOption[] = "upperdir=";
constexpr char kWorkdirOption[] = "workdir=";
@ -284,10 +288,6 @@ static bool fs_mgr_overlayfs_set_shared_mount(const std::string& mount_point, bo
if (ret) {
PERROR << "__mount(target=" << mount_point
<< ",flag=" << (shared_flag ? "MS_SHARED" : "MS_PRIVATE") << ")=" << ret;
// If "/system" doesn't look like a mountpoint, retry with "/".
if (errno == EINVAL && mount_point == "/system") {
return fs_mgr_overlayfs_set_shared_mount("/", shared_flag);
}
return false;
}
return true;
@ -374,24 +374,23 @@ static std::vector<mount_info> ReadMountinfoFromFile(const std::string& path) {
return info;
}
static bool fs_mgr_overlayfs_mount(const FstabEntry& entry) {
const auto mount_point = fs_mgr_mount_point(entry.mount_point);
const auto options = fs_mgr_get_overlayfs_options(entry);
static bool fs_mgr_overlayfs_mount_one(const FstabEntry& fstab_entry) {
const auto mount_point = fs_mgr_mount_point(fstab_entry.mount_point);
const auto options = fs_mgr_get_overlayfs_options(fstab_entry);
if (options.empty()) return false;
auto retval = true;
struct MoveEntry {
std::string mount_point;
std::string dir;
bool shared_flag;
};
std::vector<MoveEntry> moved_mounts;
auto parent_private = false;
auto parent_made_private = false;
auto dev_private = false;
auto dev_made_private = false;
bool retval = true;
bool move_dir_shared = true;
bool parent_shared = true;
bool root_shared = true;
bool root_made_private = false;
// There could be multiple mount entries with the same mountpoint.
// Group these entries together with stable_sort, and keep only the last entry of a group.
@ -411,18 +410,32 @@ static bool fs_mgr_overlayfs_mount(const FstabEntry& entry) {
// mountinfo is reversed twice, so still is in lexical sorted order.
for (const auto& entry : mountinfo) {
if ((entry.mount_point == mount_point) && !entry.shared_flag) {
parent_private = true;
if (entry.mount_point == kMoveMountTempDir) {
move_dir_shared = entry.shared_flag;
}
if ((entry.mount_point == "/dev") && !entry.shared_flag) {
dev_private = true;
if (entry.mount_point == mount_point ||
(mount_point == "/system" && entry.mount_point == "/")) {
parent_shared = entry.shared_flag;
}
if (entry.mount_point == "/") {
root_shared = entry.shared_flag;
}
}
// Precondition is that kMoveMountTempDir is MS_PRIVATE, otherwise don't try to move any
// submount in to or out of it.
if (move_dir_shared) {
mountinfo.clear();
}
// Need to make the original mountpoint MS_PRIVATE, so that the overlayfs can be MS_MOVE.
// This could happen if its parent mount is remounted later.
if (!parent_private) {
parent_made_private = fs_mgr_overlayfs_set_shared_mount(mount_point, false);
if (!fs_mgr_overlayfs_set_shared_mount(mount_point, false)) {
// If failed to set "/system" mount type, it might be due to "/system" not being a valid
// mountpoint after switch root. Retry with "/" in this case.
if (errno == EINVAL && mount_point == "/system") {
root_made_private = fs_mgr_overlayfs_set_shared_mount("/", false);
}
}
for (const auto& entry : mountinfo) {
@ -440,8 +453,8 @@ static bool fs_mgr_overlayfs_mount(const FstabEntry& entry) {
// mountinfo is in lexical order, so no need to worry about |entry| being a parent mount of
// entries of |moved_mounts|.
// use as the bound directory in /dev.
MoveEntry new_entry{entry.mount_point, "/dev/TemporaryDir-XXXXXX", entry.shared_flag};
MoveEntry new_entry{entry.mount_point, kMoveMountTempDir + "/TemporaryDir-XXXXXX"s,
entry.shared_flag};
{
AutoSetFsCreateCon createcon;
auto new_context = fs_mgr_get_context(entry.mount_point);
@ -497,10 +510,6 @@ static bool fs_mgr_overlayfs_mount(const FstabEntry& entry) {
// Move submounts back.
for (const auto& entry : moved_mounts) {
if (!dev_private && !dev_made_private) {
dev_made_private = fs_mgr_overlayfs_set_shared_mount("/dev", false);
}
if (!fs_mgr_overlayfs_move_mount(entry.dir, entry.mount_point)) {
retval = false;
} else if (entry.shared_flag &&
@ -509,12 +518,13 @@ static bool fs_mgr_overlayfs_mount(const FstabEntry& entry) {
}
rmdir(entry.dir.c_str());
}
if (dev_made_private) {
fs_mgr_overlayfs_set_shared_mount("/dev", true);
}
if (parent_made_private) {
// If the original (overridden) mount was MS_SHARED, then set the overlayfs mount to MS_SHARED.
if (parent_shared) {
fs_mgr_overlayfs_set_shared_mount(mount_point, true);
}
if (root_shared && root_made_private) {
fs_mgr_overlayfs_set_shared_mount("/", true);
}
return retval;
}
@ -730,6 +740,25 @@ bool fs_mgr_overlayfs_mount_all(Fstab* fstab) {
if (!OverlayfsSetupAllowed()) {
return false;
}
// Ensure kMoveMountTempDir is standalone mount tree with 'private' propagation by bind mounting
// to itself and set to MS_PRIVATE.
// Otherwise mounts moved in to it would have their propagation type changed unintentionally.
// Section 5d, https://www.kernel.org/doc/Documentation/filesystems/sharedsubtree.txt
if (!fs_mgr_overlayfs_already_mounted(kMoveMountTempDir, false)) {
if (mkdir(kMoveMountTempDir, 0755) && errno != EEXIST) {
PERROR << "mkdir " << kMoveMountTempDir;
}
if (mount(kMoveMountTempDir, kMoveMountTempDir, nullptr, MS_BIND, nullptr)) {
PERROR << "bind mount " << kMoveMountTempDir;
}
}
fs_mgr_overlayfs_set_shared_mount(kMoveMountTempDir, false);
android::base::ScopeGuard umountDir([]() {
umount(kMoveMountTempDir);
rmdir(kMoveMountTempDir);
});
auto ret = true;
auto scratch_can_be_mounted = !fs_mgr_overlayfs_already_mounted(kScratchMountPoint, false);
for (const auto& entry : fs_mgr_overlayfs_candidate_list(*fstab)) {
@ -742,7 +771,7 @@ bool fs_mgr_overlayfs_mount_all(Fstab* fstab) {
scratch_can_be_mounted = false;
TryMountScratch();
}
ret &= fs_mgr_overlayfs_mount(entry);
ret &= fs_mgr_overlayfs_mount_one(entry);
}
return ret;
}