Re: [PATCH] exit: Retain nsproxy for exit_task_work() work entries

[Michal Koutný]

On Thu, Dec 09, 2021 at 03:08:26PM +0100, Christian Brauner <christian.brauner@xxxxxxxxxx> wrote:
> send_sig() isn't used that was changed in response to a review. I'm
> confused. 

Sorry for ambiguity, I meant this instance [1].

> Kill and freeze only do time permission checking at open. Why would you
> introduce another write time check?
 
Let's have a cgroup G with tasks t1,...,tn (run by user u) and some
monitoring tasks m1,...,mk belonging to a different user v != u.

Currently u can kill also the tasks of v -- I'm not sure if that's
intentional. My argument would apply if it wasn't -- it'd be suscebtible
to similar abuse, i.e. passing the opened fd to a more privileged
process to kill also v's tasks. (But if the intention is to be able to
kill anyone in the cgroup, then it likely doesn't matter.)


Michal

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/cgroup/cgroup.c?h=v5.16-rc4#n3762