From: Jacob Wen <jian.w.wen@oracle.com>
Date: Wed, 30 Jan 2019 06:55:14 +0000 (+0800)
Subject: l2tp: fix reading optional fields of L2TPv3
X-Git-Tag: v4.1.12-124.31.3~272
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=98dd8fa91bb99e075f01e5a403204c88feac583c;p=users%2Fjedix%2Flinux-maple.git

l2tp: fix reading optional fields of L2TPv3

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.wen@oracle.com>
Acked-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 4522a70db7aa5e77526a4079628578599821b193)
Signed-off-by: Brian Maly <brian.maly@oracle.com>

Conflicts:
	net/l2tp/l2tp_core.c
	net/l2tp/l2tp_ip.c
	net/l2tp/l2tp_ip6.c
Commit 2b139e6b1ec8 ("l2tp: remove ->recv_payload_hook") is not in UEK5.

l2tp_core.h:
    s/l2tp_get_l2specific_len(session)/session->l2specific_len/ due to
    62e7b6a57c7b ("l2tp: remove l2specific_len dependency in l2tp_core")
    is not in UEK4.

Orabug: 29368048

Signed-off-by: Jacob Wen <jian.w.wen@oracle.com>
Reviewed-by: Junxiao Bi <junxiao.bi@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>
---

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index d37089ca31a2..61f6c8c2af58 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -929,6 +929,10 @@ 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, payload_hook);
 
 	return 0;
diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
index 68aa9ffd4ae4..4b85754c39d5 100644
--- a/net/l2tp/l2tp_core.h
+++ b/net/l2tp/l2tp_core.h
@@ -308,6 +308,26 @@ do {									\
 #define l2tp_session_dec_refcount(s) l2tp_session_dec_refcount_1(s)
 #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 + session->l2specific_len;
+
+	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 0a7a33e50461..812e9d92c92c 100644
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -160,6 +160,9 @@ 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;
+
 	l2tp_recv_common(session, skb, ptr, optr, 0, skb->len, tunnel->recv_payload_hook);
 
 	return 0;
diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
index decd6753cfac..3f973bb4ab7d 100644
--- a/net/l2tp/l2tp_ip6.c
+++ b/net/l2tp/l2tp_ip6.c
@@ -172,6 +172,9 @@ 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;
+
 	l2tp_recv_common(session, skb, ptr, optr, 0, skb->len,
 			 tunnel->recv_payload_hook);
 	return 0;