On Sat, 2024-02-17 at 00:43 +0100, Justin Iurman wrote:
> 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().
>
> Fixes: 9ee11f0fff20 ("ipv6: ioam: Data plane support for Pre-allocated Trace ")
> Reported-by: Paolo Abeni <pabeni@xxxxxxxxxx>
> Signed-off-by: Justin Iurman <justin.iurman@xxxxxxxxx>
> ---
> net/ipv6/exthdrs.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
> index 4952ae792450..f68e5faab3aa 100644
> --- a/net/ipv6/exthdrs.c
> +++ b/net/ipv6/exthdrs.c
> @@ -943,6 +943,14 @@ static bool ipv6_hop_ioam(struct sk_buff *skb, int optoff)
> if (!skb_valid_dst(skb))
> ip6_route_input(skb);
>
> + if (skb_cloned(skb)) {
> + if (pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
> + goto drop;
My personal preference would be for using skb_ensure_writable() here,
with write_len == optoff + hdr->opt_len.
> +
> + hdr = (struct ioam6_hdr *)(skb_network_header(skb) + optoff);
> + trace = (struct ioam6_trace_hdr *)((u8 *)hdr + sizeof(*hdr));
Note that this can potentially change the network header ptr and the
caller - ip6_parse_tlv() - has cached such value in 'nh'. You also need
to update ip6_parse_tlv() to reload such pointer.
Side note: a bunch of self-tests are apparently stuck after this
series. I think it's an unrelated problem. I'll try to have a better
look.
Cheers,
Paolo
