diff options
| author | Tejun Heo <tj@kernel.org> | 2023-03-14 11:59:49 -1000 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2023-03-14 16:56:20 -0700 |
| commit | b8a2e3f93d412114a1539ea97b59b3e6ed6e1f9a (patch) | |
| tree | c4255c9e3f13cbc6914cabe13e8f2296a2eb0f87 /kernel/cgroup | |
| parent | 3c2611bac08a834697be918ac357eaff2e47d5b3 (diff) | |
cgroup: Make current_cgns_cgroup_dfl() safe to call after exit_task_namespace()
The commit 332ea1f697be ("bpf: Add bpf_cgroup_from_id() kfunc") added
bpf_cgroup_from_id() which calls current_cgns_cgroup_dfl() through
cgroup_get_from_id(). However, BPF programs may be attached to a point where
current->nsproxy has already been cleared to NULL by exit_task_namespace()
and calling bpf_cgroup_from_id() would cause an oops.
Just return the system-wide root if nsproxy has been cleared. This allows
all cgroups to be looked up after the task passed through
exit_task_namespace(), which semantically makes sense. Given that the only
way to get this behavior is through BPF programs, it seems safe but let's
see what others think.
Fixes: 332ea1f697be ("bpf: Add bpf_cgroup_from_id() kfunc")
Signed-off-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/ZBDuVWiFj2jiz3i8@slm.duckdns.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/cgroup')
| -rw-r--r-- | kernel/cgroup/cgroup.c | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 935e8121b21e..8a5294f4ce72 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -1465,8 +1465,18 @@ static struct cgroup *current_cgns_cgroup_dfl(void) { struct css_set *cset; - cset = current->nsproxy->cgroup_ns->root_cset; - return __cset_cgroup_from_root(cset, &cgrp_dfl_root); + if (current->nsproxy) { + cset = current->nsproxy->cgroup_ns->root_cset; + return __cset_cgroup_from_root(cset, &cgrp_dfl_root); + } else { + /* + * NOTE: This function may be called from bpf_cgroup_from_id() + * on a task which has already passed exit_task_namespaces() and + * nsproxy == NULL. Fall back to cgrp_dfl_root which will make all + * cgroups visible for lookups. + */ + return &cgrp_dfl_root.cgrp; + } } /* look up cgroup associated with given css_set on the specified hierarchy */ |