6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Enzo Matsumiya <ematsumiya@xxxxxxx>
commit e9f2517a3e18a54a3943c098d2226b245d488801 upstream.
Commit ef7134c7fc48 ("smb: client: Fix use-after-free of network namespace.")
fixed a netns UAF by manually enabled socket refcounting
(sk->sk_net_refcnt=1 and sock_inuse_add(net, 1)).
The reason the patch worked for that bug was because we now hold
references to the netns (get_net_track() gets a ref internally)
and they're properly released (internally, on __sk_destruct()),
but only because sk->sk_net_refcnt was set.
Problem:
(this happens regardless of CONFIG_NET_NS_REFCNT_TRACKER and regardless
if init_net or other)
Setting sk->sk_net_refcnt=1 *manually* and *after* socket creation is not
only out of cifs scope, but also technically wrong -- it's set conditionally
based on user (=1) vs kernel (=0) sockets. And net/ implementations
seem to base their user vs kernel space operations on it.
e.g. upon TCP socket close, the TCP timers are not cleared because
sk->sk_net_refcnt=1:
(cf. commit 151c9c724d05 ("tcp: properly terminate timers for kernel sockets"))
net/ipv4/tcp.c:
void tcp_close(struct sock *sk, long timeout)
{
lock_sock(sk);
__tcp_close(sk, timeout);
release_sock(sk);
if (!sk->sk_net_refcnt)
inet_csk_clear_xmit_timers_sync(sk);
sock_put(sk);
}
Which will throw a lockdep warning and then, as expected, deadlock on
tcp_write_timer().
A way to reproduce this is by running the reproducer from ef7134c7fc48
and then 'rmmod cifs'. A few seconds later, the deadlock/lockdep
warning shows up.
Fix:
We shouldn't mess with socket internals ourselves, so do not set
sk_net_refcnt manually.
Also change __sock_create() to sock_create_kern() for explicitness.
As for non-init_net network namespaces, we deal with it the best way
we can -- hold an extra netns reference for server->ssocket and drop it
when it's released. This ensures that the netns still exists whenever
we need to create/destroy server->ssocket, but is not directly tied to
it.
Fixes: ef7134c7fc48 ("smb: client: Fix use-after-free of network namespace.")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Enzo Matsumiya <ematsumiya@xxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/smb/client/connect.c | 36 ++++++++++++++++++++++++++----------
1 file changed, 26 insertions(+), 10 deletions(-)
--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -1003,9 +1003,13 @@ clean_demultiplex_info(struct TCP_Server
msleep(125);
if (cifs_rdma_enabled(server))
smbd_destroy(server);
+
if (server->ssocket) {
sock_release(server->ssocket);
server->ssocket = NULL;
+
+ /* Release netns reference for the socket. */
+ put_net(cifs_net_ns(server));
}
if (!list_empty(&server->pending_mid_q)) {
@@ -1054,6 +1058,7 @@ clean_demultiplex_info(struct TCP_Server
*/
}
+ /* Release netns reference for this server. */
put_net(cifs_net_ns(server));
kfree(server->leaf_fullpath);
kfree(server);
@@ -1726,6 +1731,8 @@ cifs_get_tcp_session(struct smb3_fs_cont
tcp_ses->ops = ctx->ops;
tcp_ses->vals = ctx->vals;
+
+ /* Grab netns reference for this server. */
cifs_set_net_ns(tcp_ses, get_net(current->nsproxy->net_ns));
tcp_ses->conn_id = atomic_inc_return(&tcpSesNextId);
@@ -1857,6 +1864,7 @@ smbd_connected:
out_err_crypto_release:
cifs_crypto_secmech_release(tcp_ses);
+ /* Release netns reference for this server. */
put_net(cifs_net_ns(tcp_ses));
out_err:
@@ -1865,8 +1873,10 @@ out_err:
cifs_put_tcp_session(tcp_ses->primary_server, false);
kfree(tcp_ses->hostname);
kfree(tcp_ses->leaf_fullpath);
- if (tcp_ses->ssocket)
+ if (tcp_ses->ssocket) {
sock_release(tcp_ses->ssocket);
+ put_net(cifs_net_ns(tcp_ses));
+ }
kfree(tcp_ses);
}
return ERR_PTR(rc);
@@ -3120,20 +3130,20 @@ generic_ip_connect(struct TCP_Server_Inf
socket = server->ssocket;
} else {
struct net *net = cifs_net_ns(server);
- struct sock *sk;
- rc = __sock_create(net, sfamily, SOCK_STREAM,
- IPPROTO_TCP, &server->ssocket, 1);
+ rc = sock_create_kern(net, sfamily, SOCK_STREAM, IPPROTO_TCP, &server->ssocket);
if (rc < 0) {
cifs_server_dbg(VFS, "Error %d creating socket\n", rc);
return rc;
}
- sk = server->ssocket->sk;
- __netns_tracker_free(net, &sk->ns_tracker, false);
- sk->sk_net_refcnt = 1;
- get_net_track(net, &sk->ns_tracker, GFP_KERNEL);
- sock_inuse_add(net, 1);
+ /*
+ * Grab netns reference for the socket.
+ *
+ * It'll be released here, on error, or in clean_demultiplex_info() upon server
+ * teardown.
+ */
+ get_net(net);
/* BB other socket options to set KEEPALIVE, NODELAY? */
cifs_dbg(FYI, "Socket created\n");
@@ -3147,8 +3157,10 @@ generic_ip_connect(struct TCP_Server_Inf
}
rc = bind_socket(server);
- if (rc < 0)
+ if (rc < 0) {
+ put_net(cifs_net_ns(server));
return rc;
+ }
/*
* Eventually check for other socket options to change from
@@ -3185,6 +3197,7 @@ generic_ip_connect(struct TCP_Server_Inf
if (rc < 0) {
cifs_dbg(FYI, "Error %d connecting to server\n", rc);
trace_smb3_connect_err(server->hostname, server->conn_id, &server->dstaddr, rc);
+ put_net(cifs_net_ns(server));
sock_release(socket);
server->ssocket = NULL;
return rc;
@@ -3193,6 +3206,9 @@ generic_ip_connect(struct TCP_Server_Inf
if (sport == htons(RFC1001_PORT))
rc = ip_rfc1001_connect(server);
+ if (rc < 0)
+ put_net(cifs_net_ns(server));
+
return rc;
}
