cgroup/bpf: only cgroup v2 can be attached by bpf programs

Only cgroup v2 can be attached by bpf programs, so this patch introduces
that cgroup_bpf_inherit and cgroup_bpf_offline can only be called in
cgroup v2, and this can fix the memleak mentioned by commit 04f8ef5643bc
("cgroup: Fix memory leak caused by missing cgroup_bpf_offline"), which
has been reverted.

Fixes: 2b0d3d3e4fcf ("percpu_ref: reduce memory footprint of percpu_ref in fast path")
Fixes: 4bfc0bb2c60e ("bpf: decouple the lifetime of cgroup_bpf from cgroup itself")
Link: https://lore.kernel.org/cgroups/aka2hk5jsel5zomucpwlxsej6iwnfw4qu5jkrmjhyfhesjlfdw@46zxhg5bdnr7/
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 5c6d32054e077f8a4067fd0b2d75736ac4a84f22..0758bf0c946862e03bc45f6eaa06292c7710366f 100644 (file)
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -2140,8 +2140,10 @@ int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
        if (ret)
                goto exit_stats;
 
-       ret = cgroup_bpf_inherit(root_cgrp);
-       WARN_ON_ONCE(ret);
+       if (root == &cgrp_dfl_root) {
+               ret = cgroup_bpf_inherit(root_cgrp);
+               WARN_ON_ONCE(ret);
+       }
 
        trace_cgroup_setup_root(root);
 
@@ -5708,9 +5710,11 @@ static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
        if (ret)
                goto out_kernfs_remove;
 
-       ret = cgroup_bpf_inherit(cgrp);
-       if (ret)
-               goto out_psi_free;
+       if (cgrp->root == &cgrp_dfl_root) {
+               ret = cgroup_bpf_inherit(cgrp);
+               if (ret)
+                       goto out_psi_free;
+       }
 
        /*
         * New cgroup inherits effective freeze counter, and
@@ -6024,7 +6028,8 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
 
        cgroup1_check_for_release(parent);
 
-       cgroup_bpf_offline(cgrp);
+       if (cgrp->root == &cgrp_dfl_root)
+               cgroup_bpf_offline(cgrp);
 
        /* put the base reference */
        percpu_ref_kill(&cgrp->self.refcnt);