Comment 27 for bug 1525915

Thank Erno for the details. Since this only breaks use-cases that actually abuse glance immutability I assume this is really a fix that stable branch needs.

Here is another impact description draft, hopefully more clear and simple:

Title: Glance image status manipulation through locations removal
Reporter: Erno Kuvaja (HPE)
Products: Glance
Affects: <=2015.1.2, >=11.0.0 <= 11.0.1

Description:
Erno Kuvaja from HPE reported a vulnerability in Glance. By removing the last location of an image, an authenticated user may change the image status back to queued and may be able to upload new image data resulting in a broken Glance's immutability promise. A malicious tenant may exploit this flaw to silently replace image data it owns, regardless of the original creator or the visibility settings. Only setups with show_multiple_locations enabled (not default) are affected.

Pre-OSSA Note:
The proposed fix prevents the removal of the last location of an image so that an active image is always available. This action was previously incorrectly allowed and the fix might break some users who are relying on the false assumption that it would be ok to replace the data of existing image in the special case that the multiple locations has been configured.