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Commit 5ede70f7 authored by Kelvin Zhang's avatar Kelvin Zhang
Browse files

Mount /data as readonly before encrypt_inplace 

According to aosp/1908136, the current flow is

1. factory reset formatted raw disk.
2. next boot tries to convert it to metadata encryption
2.a mount sda27
2.b umount sda27
2.c encrypt_inplace()
2.d fsck on dm-x
2.e mount dm-x

If there are some write file operations between 2.a and 2.b, encryption
might fail. To mitigate, change the mount in 2.a to readonly if we know
we are going to do encrypt_inplace.

Test: th
Bug: 313962438
Change-Id: I7f4bbd36e1e6c978dde84f5396ffb90bbbdcae87
parent 6687cb65

fs_mgr/fs_mgr.cpp

+20 −9
Original line number Diff line number Diff line
@@ -16,7 +16,6 @@ 


#include "fs_mgr.h"



#include <ctype.h>

#include <dirent.h>

#include <errno.h>

#include <fcntl.h>
@@ -819,9 +818,13 @@ bool fs_mgr_is_device_unlocked() { 
// __mount(): wrapper around the mount() system call which also

// sets the underlying block device to read-only if the mount is read-only.

// See "man 2 mount" for return values.

static int __mount(const std::string& source, const std::string& target, const FstabEntry& entry) {

static int __mount(const std::string& source, const std::string& target, const FstabEntry& entry,

                   bool read_only = false) {

    errno = 0;

    unsigned long mountflags = entry.flags;

    if (read_only) {

        mountflags |= MS_RDONLY;

    }

    int ret = 0;

    int save_errno = 0;

    int gc_allowance = 0;
@@ -915,6 +918,10 @@ static bool fs_match(const std::string& in1, const std::string& in2) { 
    return true;

}



static bool should_use_metadata_encryption(const FstabEntry& entry) {

    return !entry.metadata_key_dir.empty() && entry.fs_mgr_flags.file_encryption;

}



// Tries to mount any of the consecutive fstab entries that match

// the mountpoint of the one given by fstab[start_idx].

//
@@ -922,8 +929,7 @@ static bool fs_match(const std::string& in1, const std::string& in2) { 
// attempted_idx: On return, will indicate which fstab entry

//     succeeded. In case of failure, it will be the start_idx.

// Sets errno to match the 1st mount failure on failure.

static bool mount_with_alternatives(Fstab& fstab, int start_idx, int* end_idx,

                                    int* attempted_idx) {

static bool mount_with_alternatives(Fstab& fstab, int start_idx, int* end_idx, int* attempted_idx) {

    unsigned long i;

    int mount_errno = 0;

    bool mounted = false;
@@ -961,8 +967,15 @@ static bool mount_with_alternatives(Fstab& fstab, int start_idx, int* end_idx, 
        }



        int retry_count = 2;

        const auto read_only = should_use_metadata_encryption(fstab[i]);

        if (read_only) {

            LOG(INFO) << "Mount point " << fstab[i].blk_device << " @ " << fstab[i].mount_point

                      << " uses metadata encryption, which means we need to unmount it later and "

                         "call encryptFstab/encrypt_inplace. To avoid file operations before "

                         "encryption, we will mount it as read-only first";

        }

        while (retry_count-- > 0) {

            if (!__mount(fstab[i].blk_device, fstab[i].mount_point, fstab[i])) {

            if (!__mount(fstab[i].blk_device, fstab[i].mount_point, fstab[i], read_only)) {

                *attempted_idx = i;

                mounted = true;

                if (i != start_idx) {
@@ -1054,10 +1067,6 @@ static bool TranslateExtLabels(FstabEntry* entry) { 
    return false;

}



static bool should_use_metadata_encryption(const FstabEntry& entry) {

    return !entry.metadata_key_dir.empty() && entry.fs_mgr_flags.file_encryption;

}



// Check to see if a mountable volume has encryption requirements

static int handle_encryptable(const FstabEntry& entry) {

    if (should_use_metadata_encryption(entry)) {
@@ -1978,6 +1987,8 @@ int fs_mgr_do_mount(Fstab* fstab, const std::string& n_name, const std::string& 
                if (retry_count <= 0) break;  // run check_fs only once

                if (!first_mount_errno) first_mount_errno = errno;

                mount_errors++;

                PERROR << "Cannot mount filesystem on " << n_blk_device << " at " << mount_point

                       << " with fstype " << fstab_entry.fs_type;

                fs_stat |= FS_STAT_FULL_MOUNT_FAILED;

                // try again after fsck

                check_fs(n_blk_device, fstab_entry.fs_type, mount_point, &fs_stat);