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sdcard: Support sdcardfs

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Add ability to use sdcardfs if kernel support is found.
In the future, we will likely remove the fuse components
entirely, but for now, just use sdcardfs when possible.

Bug: 19160983
Change-Id: I35e4d6cb5976c00c6f87ff7fc478ba9f9d212c05
Signed-off-by: Daniel Rosenberg <drosen@google.com>
This commit is contained in:
Daniel Rosenberg 2016-02-26 14:21:12 -08:00
parent 4edec25396
commit 2bd0efa89c
1 changed files with 104 additions and 1 deletions
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105
sdcard/sdcard.c
View file

@ -1894,6 +1894,105 @@ static void run(const char* source_path, const char* label, uid_t uid,
exit(1);
}
static int sdcardfs_setup(const char *source_path, const char *dest_path, uid_t fsuid,
gid_t fsgid, bool multi_user, userid_t userid, gid_t gid, mode_t mask) {
char opts[256];
snprintf(opts, sizeof(opts),
"fsuid=%d,fsgid=%d,%smask=%d,userid=%d,gid=%d",
fsuid, fsgid, multi_user?"multiuser,":"", mask, userid, gid);
if (mount(source_path, dest_path, "sdcardfs",
MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_NOATIME, opts) != 0) {
ERROR("failed to mount sdcardfs filesystem: %s\n", strerror(errno));
return -1;
}
return 0;
}
static void run_sdcardfs(const char* source_path, const char* label, uid_t uid,
gid_t gid, userid_t userid, bool multi_user, bool full_write) {
char dest_path_default[PATH_MAX];
char dest_path_read[PATH_MAX];
char dest_path_write[PATH_MAX];
char obb_path[PATH_MAX];
snprintf(dest_path_default, PATH_MAX, "/mnt/runtime/default/%s", label);
snprintf(dest_path_read, PATH_MAX, "/mnt/runtime/read/%s", label);
snprintf(dest_path_write, PATH_MAX, "/mnt/runtime/write/%s", label);
umask(0);
if (multi_user) {
/* 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)
|| sdcardfs_setup(source_path, dest_path_read, uid, gid, multi_user, userid,
AID_EVERYBODY, 0027)
|| sdcardfs_setup(source_path, dest_path_write, uid, gid, multi_user, userid,
AID_EVERYBODY, full_write ? 0007 : 0027)) {
ERROR("failed to fuse_setup\n");
exit(1);
}
} else {
/* Physical storage is readable by all users on device, but
* 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)
|| sdcardfs_setup(source_path, dest_path_read, uid, gid, multi_user, userid,
AID_EVERYBODY, full_write ? 0027 : 0022)
|| sdcardfs_setup(source_path, dest_path_write, uid, gid, multi_user, userid,
AID_EVERYBODY, full_write ? 0007 : 0022)) {
ERROR("failed to fuse_setup\n");
exit(1);
}
}
/* Drop privs */
if (setgroups(sizeof(kGroups) / sizeof(kGroups[0]), kGroups) < 0) {
ERROR("cannot setgroups: %s\n", strerror(errno));
exit(1);
}
if (setgid(gid) < 0) {
ERROR("cannot setgid: %s\n", strerror(errno));
exit(1);
}
if (setuid(uid) < 0) {
ERROR("cannot setuid: %s\n", strerror(errno));
exit(1);
}
if (multi_user) {
snprintf(obb_path, sizeof(obb_path), "%s/obb", source_path);
fs_prepare_dir(&obb_path[0], 0775, uid, gid);
}
exit(0);
}
static bool supports_sdcardfs(void) {
FILE *fp;
char *buf = NULL;
size_t buflen = 0;
fp = fopen("/proc/filesystems", "r");
if (!fp) {
ERROR("Could not read /proc/filesystems, error: %s\n", strerror(errno));
return false;
}
while ((getline(&buf, &buflen, fp)) > 0) {
if (strstr(buf, "sdcardfs\n")) {
free(buf);
fclose(fp);
return true;
}
}
free(buf);
fclose(fp);
return false;
}
int main(int argc, char **argv) {
const char *source_path = NULL;
const char *label = NULL;
@ -1966,6 +2065,10 @@ int main(int argc, char **argv) {
sleep(1);
}
run(source_path, label, uid, gid, userid, multi_user, full_write);
if (supports_sdcardfs()) {
run_sdcardfs(source_path, label, uid, gid, userid, multi_user, full_write);
} else {
run(source_path, label, uid, gid, userid, multi_user, full_write);
}
return 1;
}