Re: A user cannot remove his readonly snapshots?!

[Goffredo Baroncelli <kreijack@libero.it>]

On 09/16/2017 01:22 AM, Kai Krakow wrote:
> Am Sat, 16 Sep 2017 00:02:01 +0200
> schrieb Ulli Horlacher <framstag@rus.uni-stuttgart.de>:
> 
>> On Fri 2017-09-15 (23:44), Ulli Horlacher wrote:
[...]
> 
> See "man mount" in section btrfs mount options: There is a mount option
> to allow normal user to delete snapshots. But this is said to has
> security implication I cannot currently tell. Maybe someone else knows.

"btrfs sub del" removes a subvolume independently by its contents: it doesn't check the subvolume files/directories and their permission/ownership. 

This is different from a "rm -rf", which (e.g.) can't delete a directory owned by a different user with files

ghigo@venice:/tmp$ mkdir d
ghigo@venice:/tmp$ mkdir d/d
ghigo@venice:/tmp$ touch d/d/f
ghigo@venice:/tmp$ sudo chown nobody d/d
ghigo@venice:/tmp$ rm -rf d
rm: cannot remove 'd/d/f': Permission denied

In the past I proposed to allow an ordinary user to remove an *empty* subvolume with a simple rmdir (if he has the permissions). This would solve this kind of problem.

https://www.spinics.net/lists/linux-btrfs/msg06499.html

or to relax the check around "btrfs sub del", so an user can remove an _empty_ subvolume

https://www.spinics.net/lists/linux-btrfs/msg06522.html

> 
> 
BR
G.Baroncelli

-- 
gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D  17B2 0EDA 9B37 8B82 E0B5