[PATCH] mkfs.ubifs: Add support for symlinks in device table

[Richard Weinberger]

David,

Am 18.05.2017 um 17:16 schrieb David Engraf:
> Hi Richard,
> 
> Am 18.05.2017 um 17:08 schrieb Richard Weinberger:
>> David,
>>
>> Am 18.05.2017 um 17:03 schrieb David Engraf:
>>>>> You're right the permissions are ignored for symlinks but the user and group id is used. Without this flag mkfs.ubifs takes uid/gid from the local system.
>>>>
>>>> IMHO we can just force the uid/gid to 0, no?
>>>
>>> Why? It doesn't make sense to have all uid/gid to 0. This should be decided by the user. The purpose of the device table file is to allow the user to specify the
>>> permissions/uid/gid to his requirements. mkfs.jffs2 handles it like that as well.
>>
>> Since the ownership is ignored too, what is the usecase?
> 
> The ownership is not ignored, you can have a different one for a symlink (check "chown -h"). This is supported on ubifs:
> 
> lrwxrwxrwx    1 1        1     9 Jan  1 00:00 link -> orig_file
> -rw-r--r--    1 0        0     0 Jan  1 00:00 orig_file

Ignored in terms of not evaluated.

i.e.
rw at captainhero:/mnt/dir> id
uid=1000(rw) gid=100(users) groups=100(users)
rw at captainhero:/mnt/dir> ls -la
total 0
drwxr-xr-x 2 rw   root 240 May 18 17:23 .
drwxr-xr-x 3 root root 224 May 18 17:22 ..
lrwxrwxrwx 1 root root  11 May 18 17:23 s -> /etc/shadow
rw at captainhero:/mnt/dir> rm s
rw at captainhero:/mnt/dir> ls -la
total 0
drwxr-xr-x 2 rw   root 176 May 18 17:24 .
drwxr-xr-x 3 root root 224 May 18 17:22 ..
rw at captainhero:/mnt/dir>

Although, user rw is not root, it can delete "s" which is owned by root
because rw has write permission on /mnt/dir.

That's why I'm interested in the usecase.

Thanks,
//richard