diff options
| author | Luxiao Xu <rakukuip@gmail.com> | 2026-08-12 20:54:38 +0800 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-08-17 13:15:09 -0700 |
| commit | d0d48d999b0eee6bb176ef4e39d9be868fa80f7e (patch) | |
| tree | 49949bae0ab6802ea016f3cf16f7f0dfe5ff01ce | |
| parent | c786f61135cae5cad1ca12aabc8ec47499fa8097 (diff) | |
| download | linux-d0d48d999b0eee6bb176ef4e39d9be868fa80f7e.tar.gz linux-d0d48d999b0eee6bb176ef4e39d9be868fa80f7e.zip | |
ipv6: fix use-after-free in ip6_finish_output2()
ip6_finish_output2() caches a pointer to the IPv6 destination
address (daddr) before invoking lwtunnel_xmit(). The LWT-BPF
transmit path or other encapsulation operations within
lwtunnel_xmit() can reallocate the skb head, freeing the memory
that daddr points to. When lwtunnel_xmit() returns
LWTUNNEL_XMIT_CONTINUE, the function continues to use the stale
daddr pointer to compute the nexthop and to look up or create the
neighbour entry. This results in a use-after-free read, which can
leak sensitive kernel data, pollute the neighbour table with
arbitrary values, misdirect traffic, or crash the system.
Fix this by re-fetching the IPv6 header and the destination
address pointer after lwtunnel_xmit() returns
LWTUNNEL_XMIT_CONTINUE, ensuring that the subsequent nexthop
computation and neighbour lookup operate on valid memory.
Fixes: e415ed3a4b8b ("ipv6: use skb_expand_head in ip6_finish_output2")
Cc: stable@vger.kernel.org
Reported-by: Vega <vega@nebusec.ai>
Signed-off-by: Luxiao Xu <rakukuip@gmail.com>
Signed-off-by: Ren Wei <weir@nebusec.ai>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/4aa3f53bc44e79572c6dd2340ec7b68ef1a3d87d.1786516730.git.rakukuip@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | net/ipv6/ip6_output.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 2c44e5ed6171..8fc4766c8da9 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -116,6 +116,8 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff * if (res != LWTUNNEL_XMIT_CONTINUE) return res; + hdr = ipv6_hdr(skb); + daddr = &hdr->daddr; } IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_OUT, skb->len); |