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authorTom Parkin <tparkin@katalix.com>2013-03-19 06:11:22 +0000
committerDavid S. Miller <davem@davemloft.net>2013-03-20 12:10:39 -0400
commit7b7c0719cd7afee725b920d75ec6a500b76107e6 (patch)
tree4ea11a15d2ee815f62d649257a8491870a382504 /net/l2tp/l2tp_netlink.c
parentcf2f5c886a209377daefd5d2ba0bcd49c3887813 (diff)
l2tp: avoid deadlock in l2tp stats update
l2tp's u64_stats writers were incorrectly synchronised, making it possible to deadlock a 64bit machine running a 32bit kernel simply by sending the l2tp code netlink commands while passing data through l2tp sessions. Previous discussion on netdev determined that alternative solutions such as spinlock writer synchronisation or per-cpu data would bring unjustified overhead, given that most users interested in high volume traffic will likely be running 64bit kernels on 64bit hardware. As such, this patch replaces l2tp's use of u64_stats with atomic_long_t, thereby avoiding the deadlock. Ref: http://marc.info/?l=linux-netdev&m=134029167910731&w=2 http://marc.info/?l=linux-netdev&m=134079868111131&w=2 Signed-off-by: Tom Parkin <tparkin@katalix.com> Signed-off-by: James Chapman <jchapman@katalix.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/l2tp/l2tp_netlink.c')
-rw-r--r--net/l2tp/l2tp_netlink.c72
1 files changed, 28 insertions, 44 deletions
diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
index c1bab22db85e..0825ff26e113 100644
--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -246,8 +246,6 @@ static int l2tp_nl_tunnel_send(struct sk_buff *skb, u32 portid, u32 seq, int fla
#if IS_ENABLED(CONFIG_IPV6)
struct ipv6_pinfo *np = NULL;
#endif
- struct l2tp_stats stats;
- unsigned int start;
hdr = genlmsg_put(skb, portid, seq, &l2tp_nl_family, flags,
L2TP_CMD_TUNNEL_GET);
@@ -265,28 +263,22 @@ static int l2tp_nl_tunnel_send(struct sk_buff *skb, u32 portid, u32 seq, int fla
if (nest == NULL)
goto nla_put_failure;
- do {
- start = u64_stats_fetch_begin(&tunnel->stats.syncp);
- stats.tx_packets = tunnel->stats.tx_packets;
- stats.tx_bytes = tunnel->stats.tx_bytes;
- stats.tx_errors = tunnel->stats.tx_errors;
- stats.rx_packets = tunnel->stats.rx_packets;
- stats.rx_bytes = tunnel->stats.rx_bytes;
- stats.rx_errors = tunnel->stats.rx_errors;
- stats.rx_seq_discards = tunnel->stats.rx_seq_discards;
- stats.rx_oos_packets = tunnel->stats.rx_oos_packets;
- } while (u64_stats_fetch_retry(&tunnel->stats.syncp, start));
-
- if (nla_put_u64(skb, L2TP_ATTR_TX_PACKETS, stats.tx_packets) ||
- nla_put_u64(skb, L2TP_ATTR_TX_BYTES, stats.tx_bytes) ||
- nla_put_u64(skb, L2TP_ATTR_TX_ERRORS, stats.tx_errors) ||
- nla_put_u64(skb, L2TP_ATTR_RX_PACKETS, stats.rx_packets) ||
- nla_put_u64(skb, L2TP_ATTR_RX_BYTES, stats.rx_bytes) ||
+ if (nla_put_u64(skb, L2TP_ATTR_TX_PACKETS,
+ atomic_long_read(&tunnel->stats.tx_packets)) ||
+ nla_put_u64(skb, L2TP_ATTR_TX_BYTES,
+ atomic_long_read(&tunnel->stats.tx_bytes)) ||
+ nla_put_u64(skb, L2TP_ATTR_TX_ERRORS,
+ atomic_long_read(&tunnel->stats.tx_errors)) ||
+ nla_put_u64(skb, L2TP_ATTR_RX_PACKETS,
+ atomic_long_read(&tunnel->stats.rx_packets)) ||
+ nla_put_u64(skb, L2TP_ATTR_RX_BYTES,
+ atomic_long_read(&tunnel->stats.rx_bytes)) ||
nla_put_u64(skb, L2TP_ATTR_RX_SEQ_DISCARDS,
- stats.rx_seq_discards) ||
+ atomic_long_read(&tunnel->stats.rx_seq_discards)) ||
nla_put_u64(skb, L2TP_ATTR_RX_OOS_PACKETS,
- stats.rx_oos_packets) ||
- nla_put_u64(skb, L2TP_ATTR_RX_ERRORS, stats.rx_errors))
+ atomic_long_read(&tunnel->stats.rx_oos_packets)) ||
+ nla_put_u64(skb, L2TP_ATTR_RX_ERRORS,
+ atomic_long_read(&tunnel->stats.rx_errors)))
goto nla_put_failure;
nla_nest_end(skb, nest);
@@ -612,8 +604,6 @@ static int l2tp_nl_session_send(struct sk_buff *skb, u32 portid, u32 seq, int fl
struct nlattr *nest;
struct l2tp_tunnel *tunnel = session->tunnel;
struct sock *sk = NULL;
- struct l2tp_stats stats;
- unsigned int start;
sk = tunnel->sock;
@@ -656,28 +646,22 @@ static int l2tp_nl_session_send(struct sk_buff *skb, u32 portid, u32 seq, int fl
if (nest == NULL)
goto nla_put_failure;
- do {
- start = u64_stats_fetch_begin(&session->stats.syncp);
- stats.tx_packets = session->stats.tx_packets;
- stats.tx_bytes = session->stats.tx_bytes;
- stats.tx_errors = session->stats.tx_errors;
- stats.rx_packets = session->stats.rx_packets;
- stats.rx_bytes = session->stats.rx_bytes;
- stats.rx_errors = session->stats.rx_errors;
- stats.rx_seq_discards = session->stats.rx_seq_discards;
- stats.rx_oos_packets = session->stats.rx_oos_packets;
- } while (u64_stats_fetch_retry(&session->stats.syncp, start));
-
- if (nla_put_u64(skb, L2TP_ATTR_TX_PACKETS, stats.tx_packets) ||
- nla_put_u64(skb, L2TP_ATTR_TX_BYTES, stats.tx_bytes) ||
- nla_put_u64(skb, L2TP_ATTR_TX_ERRORS, stats.tx_errors) ||
- nla_put_u64(skb, L2TP_ATTR_RX_PACKETS, stats.rx_packets) ||
- nla_put_u64(skb, L2TP_ATTR_RX_BYTES, stats.rx_bytes) ||
+ if (nla_put_u64(skb, L2TP_ATTR_TX_PACKETS,
+ atomic_long_read(&session->stats.tx_packets)) ||
+ nla_put_u64(skb, L2TP_ATTR_TX_BYTES,
+ atomic_long_read(&session->stats.tx_bytes)) ||
+ nla_put_u64(skb, L2TP_ATTR_TX_ERRORS,
+ atomic_long_read(&session->stats.tx_errors)) ||
+ nla_put_u64(skb, L2TP_ATTR_RX_PACKETS,
+ atomic_long_read(&session->stats.rx_packets)) ||
+ nla_put_u64(skb, L2TP_ATTR_RX_BYTES,
+ atomic_long_read(&session->stats.rx_bytes)) ||
nla_put_u64(skb, L2TP_ATTR_RX_SEQ_DISCARDS,
- stats.rx_seq_discards) ||
+ atomic_long_read(&session->stats.rx_seq_discards)) ||
nla_put_u64(skb, L2TP_ATTR_RX_OOS_PACKETS,
- stats.rx_oos_packets) ||
- nla_put_u64(skb, L2TP_ATTR_RX_ERRORS, stats.rx_errors))
+ atomic_long_read(&session->stats.rx_oos_packets)) ||
+ nla_put_u64(skb, L2TP_ATTR_RX_ERRORS,
+ atomic_long_read(&session->stats.rx_errors)))
goto nla_put_failure;
nla_nest_end(skb, nest);