Hi,
I got an oom panic because cgroup is leaked.
Here is the steps :
- run a docker with --cap-add sys_admin parameter and the systemd
process in the docker uses both cgroupv1 and cgroupv2
- ssh/exit from host to docker repeately
I find the number nr_dying_descendants is increasing:
linux-dVpNUK:~ # find /sys/fs/cgroup/ -name cgroup.stat -exec grep
'^nr_dying_descendants [^0]' {} +
/sys/fs/cgroup/unified/cgroup.stat:nr_dying_descendants 80
/sys/fs/cgroup/unified/system.slice/cgroup.stat:nr_dying_descendants 1
/sys/fs/cgroup/unified/system.slice/system-hostos.slice/cgroup.stat:nr_dying_descendants
1
/sys/fs/cgroup/unified/lxc/cgroup.stat:nr_dying_descendants 79
/sys/fs/cgroup/unified/lxc/5f1fdb8c54fa40c3e599613dab6e4815058b76ebada8a27bc1fe80c0d4801764/cgroup.stat:nr_dying_descendants
78
/sys/fs/cgroup/unified/lxc/5f1fdb8c54fa40c3e599613dab6e4815058b76ebada8a27bc1fe80c0d4801764/system.slice/cgroup.stat:nr_dying_descendants
78
The situation is as same as the commit bd1060a1d671 ("sock, cgroup: add
sock->sk_cgroup") describes.
"On mode switch, cgroup references which are already being pointed to by
socks may be leaked."
Do we have a fix for this leak now ?
Or how about fix this by record the cgrp2 pointer, then put it when sk
is freeing like this:
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index d9bd671105e2..cbb1e76ea305 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -770,6 +770,7 @@ struct sock_cgroup_data {
#endif
u64 val;
};
+ struct cgroup *cgrpv2;
};
/*
@@ -802,6 +803,7 @@ static inline void sock_cgroup_set_prioidx(struct
sock_cgroup_data *skcd,
return;
if (!(skcd_buf.is_data & 1)) {
+ WRITE_ONCE(skcd->cgrpv2, skcd_buf.val);
skcd_buf.val = 0;
skcd_buf.is_data = 1;
}
@@ -819,6 +821,7 @@ static inline void sock_cgroup_set_classid(struct
sock_cgroup_data *skcd,
return;
if (!(skcd_buf.is_data & 1)) {
+ WRITE_ONCE(skcd->cgrpv2, skcd_buf.val);
skcd_buf.val = 0;
skcd_buf.is_data = 1;
}
diff --git a/net/core/sock.c b/net/core/sock.c
index a0dda2bf9d7c..7c761ef2d32e 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1520,6 +1520,10 @@ static void sk_prot_free(struct proto *prot,
struct sock *sk)
slab = prot->slab;
cgroup_sk_free(&sk->sk_cgrp_data);
+ if (sk->sk_cgrp_data.cgrpv2) {
+ cgroup_put(sk->sk_cgrp_data.cgrpv2);
+ sk->sk_cgrp_data.cgrpv2 = NULL;
+ }
mem_cgroup_sk_free(sk);
security_sk_free(sk);
if (slab != NULL)
Thanks,
Yang
