On 2024/10/17 1:04, Tejun Heo wrote:
On Wed, Oct 16, 2024 at 03:13:52PM +0200, Michal Koutný wrote:
Hello.
On Wed, Oct 16, 2024 at 09:36:33AM GMT, Chen Ridong <chenridong@xxxxxxxxxxxxxxx> wrote:
As mentioned above, when cgroup_bpf_inherit returns an error in
cgroup_setup_root, cgrp->bpf.refcnt has been exited. If cgrp->bpf.refcnt is
killed again in the cgroup_kill_sb function, the data of cgrp->bpf.refcnt
may have become NULL, leading to NULL pointer dereference.
To fix this issue, goto err when cgroup_bpf_inherit returns an error.
Additionally, if cgroup_bpf_inherit returns an error after rebinding
subsystems, the root_cgrp->self.refcnt is exited, which leads to
cgroup1_root_to_use return 1 (restart) when subsystems is mounted next.
This is due to a failure trying to get the refcnt(the root is root_cgrp,
without rebinding back to cgrp_dfl_root). So move the call to
cgroup_bpf_inherit above rebind_subsystems in the cgroup_setup_root.
Fixes: 04f8ef5643bc ("cgroup: Fix memory leak caused by missing cgroup_bpf_offline")
Signed-off-by: Chen Ridong <chenridong@xxxxxxxxxx>
Hm, I always thought that BPF progs can only be attached to the default
hierarchy (cgroup_bpf_prog_attach/cgroup_get_from_fd should prevent
that).
Thus I wonder whether cgroup_bpf_inherit (which is more like
cgroup_bpf_init in this case) needs to be called no v1 roots at all (and
with such a change, 04f8ef5643bc could be effectively reverted too).
Or can bpf data be used on v1 hierarchies somehow?
We relaxed some of the usages (see cgroup_v1v2_get_from_fd()) but cgroup BPF
progs can only be attached to v2.
Thanks.
So, should commit 04f8ef5643bc ("cgroup: Fix memory leak caused by
missing cgroup_bpf_offline") be reverted, and should cgroup_bpf_inherit
be only called in v2?
Have I understood this correctly?
Best regards,
Ridong
