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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
This commit is contained in:
Jeff Sharkey 2015-07-06 09:46:08 -07:00
parent d5a84845e6
commit 25aabb9ede
1 changed files with 10 additions and 1 deletions
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11
sdcard/sdcard.c
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@ -444,7 +444,16 @@ static void derive_permissions_locked(struct fuse* fuse, struct node *parent,
/* 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: