Use pskb_may_pull() to make sure the optional fields are in skb linear
parts, so we can safely read them later.
It's easy to reproduce the issue with a net driver that supports paged
skb data. Just create a L2TPv3 over IP tunnel and then generates some
network traffic.
Once reproduced, rx err in /sys/kernel/debug/l2tp/tunnels will increase.
Changes in v4:
1. s/l2tp_v3_pull_opt/l2tp_v3_ensure_opt_in_linear/
2. s/tunnel->version != L2TP_HDR_VER_2/tunnel->version == L2TP_HDR_VER_3/
3. Add 'Fixes' in commit messages.
Changes in v3:
1. To keep consistency, move the code out of l2tp_recv_common.
2. Use "net" instead of "net-next", since this is a bug fix.
Changes in v2:
1. Only fix L2TPv3 to make code simple.
To fix both L2TPv3 and L2TPv2, we'd better refactor l2tp_recv_common.
It's complicated to do so.
2. Reloading pointers after pskb_may_pull
Fixes: f7faffa3ff8e ("l2tp: Add L2TPv3 protocol support")
Fixes: 0d76751fad77 ("l2tp: Add L2TPv3 IP encapsulation (no UDP) support")
Fixes: a32e0eec7042 ("l2tp: introduce L2TPv3 IP encapsulation support for IPv6")
Signed-off-by: Jacob Wen <jian.w....@oracle.com>
Acked-by: Guillaume Nault <gna...@redhat.com>
---
net/l2tp/l2tp_core.c | 4 ++++
net/l2tp/l2tp_core.h | 20 ++++++++++++++++++++
net/l2tp/l2tp_ip.c | 3 +++
net/l2tp/l2tp_ip6.c | 3 +++
4 files changed, 30 insertions(+)
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 26f1d435696a..dd5ba0c11ab3 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -884,6 +884,10 @@ static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel,
struct sk_buff *skb)
goto error;
}
+ if (tunnel->version == L2TP_HDR_VER_3 &&
+ l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
+ goto error;
+
l2tp_recv_common(session, skb, ptr, optr, hdrflags, length);
l2tp_session_dec_refcount(session);
diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
index 9c9afe94d389..b2ce90260c35 100644
--- a/net/l2tp/l2tp_core.h
+++ b/net/l2tp/l2tp_core.h
@@ -301,6 +301,26 @@ static inline bool l2tp_tunnel_uses_xfrm(const struct
l2tp_tunnel *tunnel)
}
#endif
+static inline int l2tp_v3_ensure_opt_in_linear(struct l2tp_session *session,
struct sk_buff *skb,
+ unsigned char **ptr, unsigned
char **optr)
+{
+ int opt_len = session->peer_cookie_len +
l2tp_get_l2specific_len(session);
+
+ if (opt_len > 0) {
+ int off = *ptr - *optr;
+
+ if (!pskb_may_pull(skb, off + opt_len))
+ return -1;
+
+ if (skb->data != *optr) {
+ *optr = skb->data;
+ *ptr = skb->data + off;
+ }
+ }
+
+ return 0;
+}
+
#define l2tp_printk(ptr, type, func, fmt, ...) \
do { \
if (((ptr)->debug) & (type)) \
diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
index 35f6f86d4dcc..d4c60523c549 100644
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -165,6 +165,9 @@ static int l2tp_ip_recv(struct sk_buff *skb)
print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, ptr, length);
}
+ if (l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
+ goto discard_sess;
+
l2tp_recv_common(session, skb, ptr, optr, 0, skb->len);
l2tp_session_dec_refcount(session);
diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
index 237f1a4a0b0c..0ae6899edac0 100644
--- a/net/l2tp/l2tp_ip6.c
+++ b/net/l2tp/l2tp_ip6.c
@@ -178,6 +178,9 @@ static int l2tp_ip6_recv(struct sk_buff *skb)
print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, ptr, length);
}
+ if (l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
+ goto discard_sess;
+
l2tp_recv_common(session, skb, ptr, optr, 0, skb->len);
l2tp_session_dec_refcount(session);
--
2.17.1
