[PATCH 6.6 284/299] Fix write to cloned skb in ipv6_hop_ioam()

Greg Kroah-Hartman
2024-02-27T14:00:04Z

From: Justin Iurman <justin.iurman@uliege.be>

[ Upstream commit f198d933c2e4f8f89e0620fbaf1ea7eac384a0eb ]

ioam6_fill_trace_data() writes inside the skb payload without ensuring
it's writeable (e.g., not cloned). This function is called both from the
input and output path. The output path (ioam6_iptunnel) already does the
check. This commit provides a fix for the input path, inside
ipv6_hop_ioam(). It also updates ip6_parse_tlv() to refresh the network
header pointer ("nh") when returning from ipv6_hop_ioam().

Fixes: 9ee11f0fff20 ("ipv6: ioam: Data plane support for Pre-allocated Trace")
Reported-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Justin Iurman <justin.iurman@uliege.be>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv6/exthdrs.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
index 4952ae7924505..02e9ffb63af19 100644
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -177,6 +177,8 @@ static bool ip6_parse_tlv(bool hopbyhop,
case IPV6_TLV_IOAM:
if (!ipv6_hop_ioam(skb, off))
return false;
+
+ nh = skb_network_header(skb);
break;
case IPV6_TLV_JUMBO:
if (!ipv6_hop_jumbo(skb, off))
@@ -943,6 +945,14 @@ static bool ipv6_hop_ioam(struct sk_buff *skb, int optoff)
if (!skb_valid_dst(skb))
ip6_route_input(skb);

+ /* About to mangle packet header */
+ if (skb_ensure_writable(skb, optoff + 2 + hdr->opt_len))
+ goto drop;
+
+ /* Trace pointer may have changed */
+ trace = (struct ioam6_trace_hdr *)(skb_network_header(skb)
+ + optoff + sizeof(*hdr));
+
ioam6_fill_trace_data(skb, ns, trace, true);
break;
default:
--
2.43.0