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fs_mgr_overlayfs: Fix "/" mount propagation type after remount

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If remounting "/system" caused "/" to be set to MS_PRIVATE, restore it
to MS_SHARED after remount.

Bug: 306124139
Test: adb-remount-test
Test: remount /system and verify /proc/self/mountinfo
Change-Id: I12bc2ccdaf7d2b2de330064b61a8533b96defe00
This commit is contained in:
Yi-Yo Chiang 2023-10-26 15:24:19 +08:00
parent 686bff6e5c
commit db620ef531
1 changed files with 15 additions and 5 deletions
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20
fs_mgr/fs_mgr_overlayfs_mount.cpp
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@ -288,10 +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;
@ -393,6 +389,8 @@ static bool fs_mgr_overlayfs_mount_one(const FstabEntry& fstab_entry) {
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.
@ -419,6 +417,9 @@ static bool fs_mgr_overlayfs_mount_one(const FstabEntry& fstab_entry) {
(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
@ -429,7 +430,13 @@ static bool fs_mgr_overlayfs_mount_one(const FstabEntry& fstab_entry) {
// 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.
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) {
// Find all immediate submounts.
@ -515,6 +522,9 @@ static bool fs_mgr_overlayfs_mount_one(const FstabEntry& fstab_entry) {
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;
}