On Sat, Jan 23, 2021 at 12:55:16PM -0800, Maciej Żenczykowski wrote:
> From: Maciej Żenczykowski <m...@google.com>
>
> Currently a non-root process can create directories, but cannot
> create stuff in the directories it creates.
Isn't that on purpose?
>
> 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
No need for "Change-Id:" :)
> ---
> 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);
No need for (void), here, right?
And this feels like a big user-visible change, what is going to break
with this?
thanks,
greg k-h
