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    Subject[PATCH 5.15 040/207] ipv6: check return value of ipv6_skip_exthdr
    Date
    From: Jordy Zomer <jordy@pwning.systems>

    [ Upstream commit 5f9c55c8066bcd93ac25234a02585701fe2e31df ]

    The offset value is used in pointer math on skb->data.
    Since ipv6_skip_exthdr may return -1 the pointer to uh and th
    may not point to the actual udp and tcp headers and potentially
    overwrite other stuff. This is why I think this should be checked.

    EDIT: added {}'s, thanks Kees

    Signed-off-by: Jordy Zomer <jordy@pwning.systems>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/ipv6/esp6.c | 6 ++++++
    1 file changed, 6 insertions(+)

    diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
    index ed2f061b87685..f0bac6f7ab6bb 100644
    --- a/net/ipv6/esp6.c
    +++ b/net/ipv6/esp6.c
    @@ -808,6 +808,12 @@ int esp6_input_done2(struct sk_buff *skb, int err)
    struct tcphdr *th;

    offset = ipv6_skip_exthdr(skb, offset, &nexthdr, &frag_off);
    +
    + if (offset < 0) {
    + err = -EINVAL;
    + goto out;
    + }
    +
    uh = (void *)(skb->data + offset);
    th = (void *)(skb->data + offset);
    hdr_len += offset;
    --
    2.33.0


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