5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Zhiling Zou <redacted>
commit 6b222adeb9340306e2ff97127c76117abb9b3df8 upstream.
IP tunnel devices derive their advertised needed_headroom from lower
output devices. A stack of user-created devices can make the derived
value larger than the 16-bit skb header offsets can represent. Once IP
output reserves it, skb head expansion can wrap those offsets.
The runtime transmit path already caps a growing needed_headroom at 512.
Apply the same cap when tunnel configuration publishes needed_headroom
derived from a lower output device.
Capping the advertised value is safe: IP tunnel transmit still expands
the skb when a packet needs more headroom. A nonsensical stacked
configuration can therefore incur an extra reallocation, but it cannot
publish an unbounded reservation to upper layers.
Fixes: 1a37e412a022 ("net: Use 16bits for *_headers fields of struct skbuff")
Cc: <redacted>
Reported-by: Vega <redacted>
Signed-off-by: Zhiling Zou <redacted>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/ba04a1fd6bfae2377607fad5d8f80f7eb80fd4c4.1786542637.git.zhilinz@nebusec.ai (local)
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/ip_tunnels.h | 11 +++++++++--
net/ipv4/ip_tunnel.c | 2 +-
net/ipv6/ip6_gre.c | 7 +++++--
net/ipv6/ip6_tunnel.c | 7 +++++--
net/ipv6/sit.c | 2 +-
5 files changed, 21 insertions(+), 8 deletions(-)
--- a/include/net/ip_tunnels.h
+++ b/include/net/ip_tunnels.h
@@ -470,8 +470,7 @@ struct metadata_dst *iptunnel_metadata_r
int skb_tunnel_check_pmtu(struct sk_buff *skb, struct dst_entry *encap_dst,
int headroom, bool reply);
-static inline void ip_tunnel_adj_headroom(struct net_device *dev,
- unsigned int headroom)
+static inline unsigned int ip_tunnel_limit_headroom(unsigned int headroom)
{
/* we must cap headroom to some upperlimit, else pskb_expand_head
* will overflow header offsets in skb_headers_offset_update().@@ -481,6 +480,14 @@ static inline void ip_tunnel_adj_headroo
if (headroom > max_allowed)
headroom = max_allowed;
+ return headroom;
+}
+
+static inline void ip_tunnel_adj_headroom(struct net_device *dev,
+ unsigned int headroom)
+{
+ headroom = ip_tunnel_limit_headroom(headroom);
+
if (headroom > READ_ONCE(dev->needed_headroom))
WRITE_ONCE(dev->needed_headroom, headroom);
}
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c@@ -316,7 +316,7 @@ static int ip_tunnel_bind_dev(struct net
mtu = min(tdev->mtu, IP_MAX_MTU);
}
- dev->needed_headroom = t_hlen + hlen;
+ dev->needed_headroom = ip_tunnel_limit_headroom(t_hlen + hlen);
mtu -= t_hlen + (dev->type == ARPHRD_ETHER ? dev->hard_header_len : 0);
if (mtu < IPV4_MIN_MTU)
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -1151,8 +1151,11 @@ static void ip6gre_tnl_link_config_route
return;
if (rt->dst.dev) {
- dev->needed_headroom = rt->dst.dev->hard_header_len +
- t_hlen;
+ unsigned int headroom;
+
+ headroom = rt->dst.dev->hard_header_len + t_hlen;
+ headroom = ip_tunnel_limit_headroom(headroom);
+ dev->needed_headroom = headroom;
if (set_mtu) {
int mtu = rt->dst.dev->mtu - t_hlen;
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c@@ -1497,8 +1497,11 @@ static void ip6_tnl_link_config(struct i
tdev = __dev_get_by_index(t->net, p->link);
if (tdev) {
- dev->needed_headroom = tdev->hard_header_len +
- tdev->needed_headroom + t_hlen;
+ unsigned int headroom;
+
+ headroom = tdev->hard_header_len + tdev->needed_headroom;
+ headroom += t_hlen;
+ dev->needed_headroom = ip_tunnel_limit_headroom(headroom);
mtu = min_t(unsigned int, tdev->mtu, IP6_MAX_MTU);
mtu = mtu - t_hlen;
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c@@ -1139,7 +1139,7 @@ static void ipip6_tunnel_bind_dev(struct
WRITE_ONCE(dev->mtu, mtu);
hlen = tdev->hard_header_len + tdev->needed_headroom;
}
- dev->needed_headroom = t_hlen + hlen;
+ dev->needed_headroom = ip_tunnel_limit_headroom(t_hlen + hlen);
}
static void ipip6_tunnel_update(struct ip_tunnel *t, struct ip_tunnel_parm *p,