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l2tp: hold reference on tunnels printed in l2tp/tunnels debugfs file

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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: 0ad6614048 ("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>
This commit is contained in:
Guillaume Nault 2018-04-12 20:50:35 +02:00 committed by David S. Miller
parent 0e0c3fee3a
commit f726214d9b
3 changed files with 13 additions and 23 deletions
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20
net/l2tp/l2tp_core.c
View File

@ -355,26 +355,6 @@ err_tlock:
}
EXPORT_SYMBOL_GPL(l2tp_session_register);
struct l2tp_tunnel *l2tp_tunnel_find_nth(const 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
*****************************************************************************/

1
net/l2tp/l2tp_core.h
View File

@ -222,7 +222,6 @@ struct l2tp_session *l2tp_session_get(const struct net *net,
struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth);
struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
const char *ifname);
struct l2tp_tunnel *l2tp_tunnel_find_nth(const 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,

15
net/l2tp/l2tp_debugfs.c
View File

@ -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 seq_file *m, void *v, loff_t *pos)
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)