RE: [PATCH nf-next] netns: add and use net_ns_barrier
From: David Laight <hidden>
Date: 2017-06-02 09:38:22
Also in:
netfilter-devel
From: Florian Westphal
Sent: 30 May 2017 10:38 Quoting Joe Stringer: If a user loads nf_conntrack_ftp, sends FTP traffic through a network namespace, destroys that namespace then unloads the FTP helper module, then the kernel will crash. Events that lead to the crash: 1. conntrack is created with ftp helper in netns x 2. This netns is destroyed 3. netns destruction is scheduled 4. netns destruction wq starts, removes netns from global list 5. ftp helper is unloaded, which resets all helpers of the conntracks via for_each_net() but because netns is already gone from list the for_each_net() loop doesn't include it, therefore all of these conntracks are unaffected. 6. helper module unload finishes 7. netns wq invokes destructor for rmmod'ed helper
...
quoted hunk ↗ jump to hunk
void nf_ct_iterate_destroy(int (*iter)(struct nf_conn *i, void *data), void *data)@@ -1734,6 +1736,13 @@ nf_ct_iterate_destroy(int (*iter)(struct nf_conn *i, void *data), void *data) } rtnl_unlock(); + /* Need to wait for netns cleanup worker to finish, if its + * running -- it might have deleted a net namespace from + * the global list, so our __nf_ct_unconfirmed_destroy() might + * not have affected all namespaces. + */ + net_ns_barrier(); +
A problem I see is that nothing obvious guarantees that the cleanup worker has actually started. David