| From: Guillaume Nault <g.nault@alphalink.fr> |
| Date: Thu, 12 Apr 2018 20:50:35 +0200 |
| Subject: l2tp: hold reference on tunnels printed in l2tp/tunnels debugfs file |
| |
| commit f726214d9b23e5fce8c11937577a289a3202498f upstream. |
| |
| Use l2tp_tunnel_get_nth() instead of l2tp_tunnel_find_nth(), to be safe |
| against concurrent tunnel deletion. |
| |
| Use the same mechanism as in l2tp_ppp.c for dropping the reference |
| taken by l2tp_tunnel_get_nth(). That is, drop the reference just |
| before looking up the next tunnel. In case of error, drop the last |
| accessed tunnel in l2tp_dfs_seq_stop(). |
| |
| That was the last use of l2tp_tunnel_find_nth(). |
| |
| Fixes: 0ad6614048cf ("l2tp: Add debugfs files for dumping l2tp debug info") |
| Signed-off-by: Guillaume Nault <g.nault@alphalink.fr> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| [bwh: Backported to 3.16: adjust context] |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| net/l2tp/l2tp_core.c | 20 -------------------- |
| net/l2tp/l2tp_core.h | 1 - |
| net/l2tp/l2tp_debugfs.c | 15 +++++++++++++-- |
| 3 files changed, 13 insertions(+), 23 deletions(-) |
| |
| --- a/net/l2tp/l2tp_core.c |
| +++ b/net/l2tp/l2tp_core.c |
| @@ -415,26 +415,6 @@ err_tlock: |
| } |
| EXPORT_SYMBOL_GPL(l2tp_session_register); |
| |
| -struct l2tp_tunnel *l2tp_tunnel_find_nth(struct net *net, int nth) |
| -{ |
| - struct l2tp_net *pn = l2tp_pernet(net); |
| - struct l2tp_tunnel *tunnel; |
| - int count = 0; |
| - |
| - rcu_read_lock_bh(); |
| - list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) { |
| - if (++count > nth) { |
| - rcu_read_unlock_bh(); |
| - return tunnel; |
| - } |
| - } |
| - |
| - rcu_read_unlock_bh(); |
| - |
| - return NULL; |
| -} |
| -EXPORT_SYMBOL_GPL(l2tp_tunnel_find_nth); |
| - |
| /***************************************************************************** |
| * Receive data handling |
| *****************************************************************************/ |
| --- a/net/l2tp/l2tp_core.h |
| +++ b/net/l2tp/l2tp_core.h |
| @@ -242,7 +242,6 @@ struct l2tp_session *l2tp_session_get_nt |
| struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net, |
| const char *ifname, |
| bool do_ref); |
| -struct l2tp_tunnel *l2tp_tunnel_find_nth(struct net *net, int nth); |
| |
| int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, |
| u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg, |
| --- a/net/l2tp/l2tp_debugfs.c |
| +++ b/net/l2tp/l2tp_debugfs.c |
| @@ -47,7 +47,11 @@ struct l2tp_dfs_seq_data { |
| |
| static void l2tp_dfs_next_tunnel(struct l2tp_dfs_seq_data *pd) |
| { |
| - pd->tunnel = l2tp_tunnel_find_nth(pd->net, pd->tunnel_idx); |
| + /* Drop reference taken during previous invocation */ |
| + if (pd->tunnel) |
| + l2tp_tunnel_dec_refcount(pd->tunnel); |
| + |
| + pd->tunnel = l2tp_tunnel_get_nth(pd->net, pd->tunnel_idx); |
| pd->tunnel_idx++; |
| } |
| |
| @@ -96,7 +100,14 @@ static void *l2tp_dfs_seq_next(struct se |
| |
| static void l2tp_dfs_seq_stop(struct seq_file *p, void *v) |
| { |
| - /* nothing to do */ |
| + struct l2tp_dfs_seq_data *pd = v; |
| + |
| + if (!pd || pd == SEQ_START_TOKEN) |
| + return; |
| + |
| + /* Drop reference taken by last invocation of l2tp_dfs_next_tunnel() */ |
| + if (pd->tunnel) |
| + l2tp_tunnel_dec_refcount(pd->tunnel); |
| } |
| |
| static void l2tp_dfs_seq_tunnel_show(struct seq_file *m, void *v) |