29 Sep
2018
29 Sep
'18
2:25 p.m.
On Sep 29, 2018, at 3:34 AM, Aleksa Sarai cyphar@cyphar.com wrote:
The need for some sort of control over VFS's path resolution (to avoid malicious paths resulting in inadvertent breakouts) has been a very long-standing desire of many userspace applications. This patchset is a revival of Al Viro's old AT_NO_JUMPS[1] patchset with a few additions.
The most obvious change is that AT_NO_JUMPS has been split as dicussed in the original thread, along with a further split of AT_NO_PROCLINKS which means that each individual property of AT_NO_JUMPS is now a separate flag:
- Path-based escapes from the starting-point using "/" or ".." are blocked by AT_BENEATH.
Seems useful.
- Mountpoint crossings are blocked by AT_XDEV.
Seems useful.
- /proc/$pid/fd/$fd resolution is blocked by AT_NO_PROCLINKS (more correctly it actually blocks any user of nd_jump_link() because it allows out-of-VFS path resolution manipulation).
So how do I disable following symlinks? ISTM the most natural way would be to have AT_NO_SYMLINKS, and to have that flag disable proc links.