seg6: Fix validation of nexthop addresses

[ Upstream commit 7632fedb266d93ed0ed9f487133e6c6314a9b2d1 ]

The kernel currently validates that the length of the provided nexthop
address does not exceed the specified length. This can lead to the
kernel reading uninitialized memory if user space provided a shorter
length than the specified one.

Fix by validating that the provided length exactly matches the specified
one.

Fixes: d1df6fd8a1d2 ("ipv6: sr: define core operations for seg6local lightweight tunnel")
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20250604113252.371528-1-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/ipv6/seg6_local.c b/net/ipv6/seg6_local.c
index 33cb0381b5749c04dbcb70606836cf69b488b392..b7d9a68a265d7ce2f5fc614bf2348e4b5b135256 100644 (file)
--- a/net/ipv6/seg6_local.c
+++ b/net/ipv6/seg6_local.c
@@ -1250,10 +1250,8 @@ static const struct nla_policy seg6_local_policy[SEG6_LOCAL_MAX + 1] = {
        [SEG6_LOCAL_SRH]        = { .type = NLA_BINARY },
        [SEG6_LOCAL_TABLE]      = { .type = NLA_U32 },
        [SEG6_LOCAL_VRFTABLE]   = { .type = NLA_U32 },
-       [SEG6_LOCAL_NH4]        = { .type = NLA_BINARY,
-                                   .len = sizeof(struct in_addr) },
-       [SEG6_LOCAL_NH6]        = { .type = NLA_BINARY,
-                                   .len = sizeof(struct in6_addr) },
+       [SEG6_LOCAL_NH4]        = NLA_POLICY_EXACT_LEN(sizeof(struct in_addr)),
+       [SEG6_LOCAL_NH6]        = NLA_POLICY_EXACT_LEN(sizeof(struct in6_addr)),
        [SEG6_LOCAL_IIF]        = { .type = NLA_U32 },
        [SEG6_LOCAL_OIF]        = { .type = NLA_U32 },
        [SEG6_LOCAL_BPF]        = { .type = NLA_NESTED },