Hi,
On 2020/7/20 23:36, Greg Kroah-Hartman wrote:
From: Cong Wang <xiyou.wangc...@gmail.com>
[ Upstream commit ad0f75e5f57ccbceec13274e1e242f2b5a6397ed ]
When we clone a socket in sk_clone_lock(), its sk_cgrp_data is
copied, so the cgroup refcnt must be taken too. And, unlike the
sk_alloc() path, sock_update_netprioidx() is not called here.
Therefore, it is safe and necessary to grab the cgroup refcnt
even when cgroup_sk_alloc is disabled.
sk_clone_lock() is in BH context anyway, the in_interrupt()
would terminate this function if called there. And for sk_alloc()
skcd->val is always zero. So it's safe to factor out the code
to make it more readable.
The global variable 'cgroup_sk_alloc_disabled' is used to determine
whether to take these reference counts. It is impossible to make
the reference counting correct unless we save this bit of information
in skcd->val. So, add a new bit there to record whether the socket
has already taken the reference counts. This obviously relies on
kmalloc() to align cgroup pointers to at least 4 bytes,
ARCH_KMALLOC_MINALIGN is certainly larger than that.
This bug seems to be introduced since the beginning, commit
d979a39d7242 ("cgroup: duplicate cgroup reference when cloning sockets")
tried to fix it but not compeletely. It seems not easy to trigger until
the recent commit 090e28b229af
("netprio_cgroup: Fix unlimited memory leak of v2 cgroups") was merged.
Fixes: bd1060a1d671 ("sock, cgroup: add sock->sk_cgroup")
Reported-by: Cameron Berkenpas <c...@neo-zeon.de>
Reported-by: Peter Geis <pgwipe...@gmail.com>
Reported-by: Lu Fengqi <lufq.f...@cn.fujitsu.com>
Reported-by: Daniël Sonck <dsonc...@gmail.com>
Reported-by: Zhang Qiang <qiang.zh...@windriver.com>
Tested-by: Cameron Berkenpas <c...@neo-zeon.de>
Tested-by: Peter Geis <pgwipe...@gmail.com>
Tested-by: Thomas Lamprecht <t.lampre...@proxmox.com>
Cc: Daniel Borkmann <dan...@iogearbox.net>
Cc: Zefan Li <lize...@huawei.com>
Cc: Tejun Heo <t...@kernel.org>
Cc: Roman Gushchin <g...@fb.com>
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
[...]
+void cgroup_sk_clone(struct sock_cgroup_data *skcd)
+{
+ /* Socket clone path */
+ if (skcd->val) {
Compare to mainline patch, it's missing *if (skcd->no_refcnt)* check here.
Is it a mistake here ?
Thanks,
Yang
+ /*
+ * We might be cloning a socket which is left in an empty
+ * cgroup and the cgroup might have already been rmdir'd.
+ * Don't use cgroup_get_live().
+ */
+ cgroup_get(sock_cgroup_ptr(skcd));
+ }
+}
+
void cgroup_sk_free(struct sock_cgroup_data *skcd)
{
+ if (skcd->no_refcnt)
+ return;
+
cgroup_put(sock_cgroup_ptr(skcd));
}
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1694,7 +1694,7 @@ struct sock *sk_clone_lock(const struct
/* sk->sk_memcg will be populated at accept() time */
newsk->sk_memcg = NULL;
- cgroup_sk_alloc(&newsk->sk_cgrp_data);
+ cgroup_sk_clone(&newsk->sk_cgrp_data);
rcu_read_lock();
filter = rcu_dereference(sk->sk_filter);
.
