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Commit c336f862 authored by Daniel Rosenberg's avatar Daniel Rosenberg
Browse files

Add support for esdfs mounting 

If sdcardfs is turned off, try mounting esdfs.

Test: Override ro.sys.sdcardfs to be false, or run
      sm set-sdcardfs off. If the kernel contains
      esdfs, it will use it.
Bug: 63876697
Change-Id: I4db8bf336743edf62edfae41d753b1e3af163950
parent 334d2187

sdcard/sdcard.cpp

+68 −13
Original line number Diff line number Diff line
@@ -43,6 +43,44 @@ 


#include <private/android_filesystem_config.h>



#define PROP_SDCARDFS_DEVICE "ro.sys.sdcardfs"

#define PROP_SDCARDFS_USER "persist.sys.sdcardfs"



static bool supports_esdfs(void) {

    std::string filesystems;

    if (!android::base::ReadFileToString("/proc/filesystems", &filesystems)) {

        PLOG(ERROR) << "Could not read /proc/filesystems";

        return false;

    }

    for (const auto& fs : android::base::Split(filesystems, "\n")) {

        if (fs.find("esdfs") != std::string::npos) return true;

    }

    return false;

}



static bool should_use_sdcardfs(void) {

    char property[PROPERTY_VALUE_MAX];



    // Allow user to have a strong opinion about state

    property_get(PROP_SDCARDFS_USER, property, "");

    if (!strcmp(property, "force_on")) {

        LOG(WARNING) << "User explicitly enabled sdcardfs";

        return true;

    } else if (!strcmp(property, "force_off")) {

        LOG(WARNING) << "User explicitly disabled sdcardfs";

        return !supports_esdfs();

    }



    // Fall back to device opinion about state

    if (property_get_bool(PROP_SDCARDFS_DEVICE, true)) {

        LOG(WARNING) << "Device explicitly enabled sdcardfs";

        return true;

    } else {

        LOG(WARNING) << "Device explicitly disabled sdcardfs";

        return !supports_esdfs();

    }

}



// NOTE: This is a vestigial program that simply exists to mount the in-kernel

// sdcardfs filesystem.  The older FUSE-based design that used to live here has

// been completely removed to avoid confusion.
@@ -61,7 +99,7 @@ static void drop_privs(uid_t uid, gid_t gid) { 


static bool sdcardfs_setup(const std::string& source_path, const std::string& dest_path,

                           uid_t fsuid, gid_t fsgid, bool multi_user, userid_t userid, gid_t gid,

                           mode_t mask, bool derive_gid, bool default_normal) {

                           mode_t mask, bool derive_gid, bool default_normal, bool use_esdfs) {

    // Try several attempts, each time with one less option, to gracefully

    // handle older kernels that aren't updated yet.

    for (int i = 0; i < 4; i++) {
@@ -72,7 +110,7 @@ static bool sdcardfs_setup(const std::string& source_path, const std::string& de 


        auto opts = android::base::StringPrintf("fsuid=%d,fsgid=%d,%smask=%d,userid=%d,gid=%d",

                                                fsuid, fsgid, new_opts.c_str(), mask, userid, gid);

        if (mount(source_path.c_str(), dest_path.c_str(), "sdcardfs",

        if (mount(source_path.c_str(), dest_path.c_str(), use_esdfs ? "esdfs" : "sdcardfs",

                  MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_NOATIME, opts.c_str()) == -1) {

            PLOG(WARNING) << "Failed to mount sdcardfs with options " << opts;

        } else {
@@ -104,9 +142,21 @@ static bool sdcardfs_setup_bind_remount(const std::string& source_path, const st 
    return true;

}



static bool sdcardfs_setup_secondary(const std::string& default_path, const std::string& source_path,

                                     const std::string& dest_path, uid_t fsuid, gid_t fsgid,

                                     bool multi_user, userid_t userid, gid_t gid, mode_t mask,

                                     bool derive_gid, bool default_normal, bool use_esdfs) {

    if (use_esdfs) {

        return sdcardfs_setup(source_path, dest_path, fsuid, fsgid, multi_user, userid, gid, mask,

                              derive_gid, default_normal, use_esdfs);

    } else {

        return sdcardfs_setup_bind_remount(default_path, dest_path, gid, mask);

    }

}



static void run_sdcardfs(const std::string& source_path, const std::string& label, uid_t uid,

                         gid_t gid, userid_t userid, bool multi_user, bool full_write,

                         bool derive_gid, bool default_normal) {

                         bool derive_gid, bool default_normal, bool use_esdfs) {

    std::string dest_path_default = "/mnt/runtime/default/" + label;

    std::string dest_path_read = "/mnt/runtime/read/" + label;

    std::string dest_path_write = "/mnt/runtime/write/" + label;
@@ -116,10 +166,13 @@ static void run_sdcardfs(const std::string& source_path, const std::string& labe 
        // Multi-user storage is fully isolated per user, so "other"

        // permissions are completely masked off.

        if (!sdcardfs_setup(source_path, dest_path_default, uid, gid, multi_user, userid,

                            AID_SDCARD_RW, 0006, derive_gid, default_normal) ||

            !sdcardfs_setup_bind_remount(dest_path_default, dest_path_read, AID_EVERYBODY, 0027) ||

            !sdcardfs_setup_bind_remount(dest_path_default, dest_path_write, AID_EVERYBODY,

                                         full_write ? 0007 : 0027)) {

                            AID_SDCARD_RW, 0006, derive_gid, default_normal, use_esdfs) ||

            !sdcardfs_setup_secondary(dest_path_default, source_path, dest_path_read, uid, gid,

                                      multi_user, userid, AID_EVERYBODY, 0027, derive_gid,

                                      default_normal, use_esdfs) ||

            !sdcardfs_setup_secondary(dest_path_default, source_path, dest_path_write, uid, gid,

                                      multi_user, userid, AID_EVERYBODY, full_write ? 0007 : 0027,

                                      derive_gid, default_normal, use_esdfs)) {

            LOG(FATAL) << "failed to sdcardfs_setup";

        }

    } else {
@@ -127,11 +180,13 @@ static void run_sdcardfs(const std::string& source_path, const std::string& labe 
        // the Android directories are masked off to a single user

        // deep inside attr_from_stat().

        if (!sdcardfs_setup(source_path, dest_path_default, uid, gid, multi_user, userid,

                            AID_SDCARD_RW, 0006, derive_gid, default_normal) ||

            !sdcardfs_setup_bind_remount(dest_path_default, dest_path_read, AID_EVERYBODY,

                                         full_write ? 0027 : 0022) ||

            !sdcardfs_setup_bind_remount(dest_path_default, dest_path_write, AID_EVERYBODY,

                                         full_write ? 0007 : 0022)) {

                            AID_SDCARD_RW, 0006, derive_gid, default_normal, use_esdfs) ||

            !sdcardfs_setup_secondary(dest_path_default, source_path, dest_path_read, uid, gid,

                                      multi_user, userid, AID_EVERYBODY, full_write ? 0027 : 0022,

                                      derive_gid, default_normal, use_esdfs) ||

            !sdcardfs_setup_secondary(dest_path_default, source_path, dest_path_write, uid, gid,

                                      multi_user, userid, AID_EVERYBODY, full_write ? 0007 : 0022,

                                      derive_gid, default_normal, use_esdfs)) {

            LOG(FATAL) << "failed to sdcardfs_setup";

        }

    }
@@ -242,6 +297,6 @@ int main(int argc, char **argv) { 
    }



    run_sdcardfs(source_path, label, uid, gid, userid, multi_user, full_write, derive_gid,

                 default_normal);

                 default_normal, !should_use_sdcardfs());

    return 1;

}