From: Maciej Żenczykowski <m...@google.com>
Currently a non-root process can create directories, but cannot
create stuff in the directories it creates.
Example (before this patch):
phone:/ $ id
uid=1000(system) gid=1000(system) groups=1000(system),... context=u:r:su:s0
phone:/ $ cd /config/usb_gadget/g1/configs/
phone:/config/usb_gadget/g1/configs $ ls -lZ
drwxr-xr-x 3 system system u:object_r:configfs:s0 0 2020-12-28 06:03 b.1
phone:/config/usb_gadget/g1/configs $ mkdir b.2
phone:/config/usb_gadget/g1/configs $ ls -lZ
drwxr-xr-x 3 system system u:object_r:configfs:s0 0 2020-12-28 06:03 b.1
drwxr-xr-x 3 root root u:object_r:configfs:s0 0 2020-12-28 06:51 b.2
phone:/config/usb_gadget/g1/configs $ chown system:system b.2
chown: 'b.2' to 'system:system': Operation not permitted
phone:/config/usb_gadget/g1/configs $ ls -lZ b.1
-rw-r--r-- 1 system system u:object_r:configfs:s0 4096 2020-12-28 05:23
MaxPower
-rw-r--r-- 1 system system u:object_r:configfs:s0 4096 2020-12-28 05:23
bmAttributes
lrwxrwxrwx 1 root root u:object_r:configfs:s0 0 2020-12-28 05:23
function0 -> ../../../../usb_gadget/g1/functions/ffs.adb
drwxr-xr-x 2 system system u:object_r:configfs:s0 0 2020-12-28 05:23
strings
phone:/config/usb_gadget/g1/configs $ ln -s
../../../../usb_gadget/g1/functions/ffs.adb b.2/function0
ln: cannot create symbolic link from
'../../../../usb_gadget/g1/functions/ffs.adb' to 'b.2/function0': Permission
denied
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Cc: Joel Becker <jl...@evilplan.org>
Cc: Christoph Hellwig <h...@lst.de>
Signed-off-by: Maciej Żenczykowski <m...@google.com>
Change-Id: Ia907b2def940197b44aa87b337d37c5dde9c5b91
---
fs/configfs/dir.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index b839dd1b459f..04f18402ef7c 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -1410,6 +1410,21 @@ static int configfs_mkdir(struct inode *dir, struct
dentry *dentry, umode_t mode
else
ret = configfs_attach_item(parent_item, item, dentry, frag);
+ /* inherit uid/gid from process creating the directory */
+ if (!uid_eq(current_fsuid(), GLOBAL_ROOT_UID) ||
+ !gid_eq(current_fsgid(), GLOBAL_ROOT_GID)) {
+ struct inode * inode = d_inode(dentry);
+ struct iattr ia = {
+ .ia_uid = current_fsuid(),
+ .ia_gid = current_fsgid(),
+ .ia_valid = ATTR_UID | ATTR_GID,
+ };
+ inode->i_uid = ia.ia_uid;
+ inode->i_gid = ia.ia_gid;
+ /* (note: the above manual assignments skip the permission
checks) */
+ (void)configfs_setattr(dentry, &ia);
+ }
+
spin_lock(&configfs_dirent_lock);
sd->s_type &= ~CONFIGFS_USET_IN_MKDIR;
if (!ret)
--
2.30.0.280.ga3ce27912f-goog
