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ANDROID: sdcardfs: Avoid setting GIDs outside of valid ranges

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When setting up the ownership of files on the lower filesystem,
ensure that these values are in reasonable ranges for apps. If
they aren't, default to AID_MEDIA_RW

Signed-off-by: Daniel Rosenberg <drosen@google.com>
Bug: 37516160
Change-Id: I0bec76a61ac72aff0b993ab1ad04be8382178a00
This commit is contained in:
Daniel Rosenberg 2017-04-24 16:11:03 -07:00 committed by Amit Pundir
parent ecd0dfc494
commit 1e952e48ac
2 changed files with 11 additions and 4 deletions
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8
fs/sdcardfs/derived_perm.c
View file

@ -215,16 +215,16 @@ void fixup_lower_ownership(struct dentry *dentry, const char *name)
gid = AID_MEDIA_OBB;
break;
case PERM_ANDROID_PACKAGE:
if (info->d_uid != 0)
if (uid_is_app(info->d_uid))
gid = multiuser_get_ext_gid(info->d_uid);
else
gid = multiuser_get_uid(info->userid, uid);
gid = multiuser_get_uid(info->userid, AID_MEDIA_RW);
break;
case PERM_ANDROID_PACKAGE_CACHE:
if (info->d_uid != 0)
if (uid_is_app(info->d_uid))
gid = multiuser_get_ext_cache_gid(info->d_uid);
else
gid = multiuser_get_uid(info->userid, uid);
gid = multiuser_get_uid(info->userid, AID_MEDIA_RW);
break;
case PERM_PRE_ROOT:
default:

7
fs/sdcardfs/multiuser.h
View file

@ -35,6 +35,13 @@ static inline uid_t multiuser_get_uid(userid_t user_id, appid_t app_id)
return (user_id * AID_USER_OFFSET) + (app_id % AID_USER_OFFSET);
}
static inline bool uid_is_app(uid_t uid)
{
appid_t appid = uid % AID_USER_OFFSET;
return appid >= AID_APP_START && appid <= AID_APP_END;
}
static inline gid_t multiuser_get_ext_cache_gid(uid_t uid)
{
return uid - AID_APP_START + AID_EXT_CACHE_GID_START;