Commit 245426dc authored by Jacob Wen's avatar Jacob Wen Committed by Greg Kroah-Hartman

l2tp: fix reading optional fields of L2TPv3

[ Upstream commit 4522a70db7aa5e77526a4079628578599821b193 ]

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: f7faffa3 ("l2tp: Add L2TPv3 protocol support")
Fixes: 0d76751f ("l2tp: Add L2TPv3 IP encapsulation (no UDP) support")
Fixes: a32e0eec ("l2tp: introduce L2TPv3 IP encapsulation support for IPv6")
Signed-off-by: 's avatarJacob Wen <jian.w.wen@oracle.com>
Acked-by: 's avatarGuillaume Nault <gnault@redhat.com>
Signed-off-by: 's avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: 's avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f5f5d316
......@@ -930,6 +930,10 @@ 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;
......
......@@ -324,6 +324,26 @@ static inline int l2tp_get_l2specific_len(struct l2tp_session *session)
}
}
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)) \
......
......@@ -163,6 +163,9 @@ 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;
......
......@@ -174,6 +174,9 @@ 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;
......
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