Permission to view shared storage for all users.
Typical apps are restricted so they can only view shared storage
belonging to the user they're running as. However, a handful of
system components need access to shared storage across all users,
such as DefaultContainerService and SystemUI.
Since WRITE_MEDIA_STORAGE already offers this functionality by
bypassing any FUSE emulation, reuse it to grant the "sdcard_rw" GID
which is no longer handed out to third-party apps. Then we change
the FUSE daemon to allow the "sdcard_rw" GID to see shared storage
of all users.
Bug: 19995822
Change-Id: Id2fe846aefbf13fc050e9b00ddef120021e817f4
diff --git a/sdcard/sdcard.c b/sdcard/sdcard.c
index 3cd5bc4..21986fc 100644
--- a/sdcard/sdcard.c
+++ b/sdcard/sdcard.c
@@ -444,7 +444,16 @@
/* Legacy internal layout places users at top level */
node->perm = PERM_ROOT;
node->userid = strtoul(node->name, NULL, 10);
- node->gid = multiuser_get_uid(node->userid, fuse->gid);
+ if (fuse->gid == AID_SDCARD_RW) {
+ /* As an optimization, certain trusted system components only run
+ * as owner but operate across all users. Since we're now handing
+ * out the sdcard_rw GID only to trusted apps, we're okay relaxing
+ * the user boundary enforcement for the default view. The UIDs
+ * assigned to app directories are still multiuser aware. */
+ node->gid = fuse->gid;
+ } else {
+ node->gid = multiuser_get_uid(node->userid, fuse->gid);
+ }
node->mode = 0771;
break;
case PERM_ROOT: