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    Subject[PATCH 5.13 077/151] bareudp: Fix invalid read beyond skbs linear data
    Date
    From: Guillaume Nault <gnault@redhat.com>

    [ Upstream commit 143a8526ab5fd4f8a0c4fe2a9cb28c181dc5a95f ]

    Data beyond the UDP header might not be part of the skb's linear data.
    Use skb_copy_bits() instead of direct access to skb->data+X, so that
    we read the correct bytes even on a fragmented skb.

    Fixes: 4b5f67232d95 ("net: Special handling for IP & MPLS.")
    Signed-off-by: Guillaume Nault <gnault@redhat.com>
    Link: https://lore.kernel.org/r/7741c46545c6ef02e70c80a9b32814b22d9616b3.1628264975.git.gnault@redhat.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/net/bareudp.c | 16 +++++++++++-----
    1 file changed, 11 insertions(+), 5 deletions(-)

    diff --git a/drivers/net/bareudp.c b/drivers/net/bareudp.c
    index edfad93e7b68..22e26458a86e 100644
    --- a/drivers/net/bareudp.c
    +++ b/drivers/net/bareudp.c
    @@ -71,12 +71,18 @@ static int bareudp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
    family = AF_INET6;

    if (bareudp->ethertype == htons(ETH_P_IP)) {
    - struct iphdr *iphdr;
    + __u8 ipversion;

    - iphdr = (struct iphdr *)(skb->data + BAREUDP_BASE_HLEN);
    - if (iphdr->version == 4) {
    - proto = bareudp->ethertype;
    - } else if (bareudp->multi_proto_mode && (iphdr->version == 6)) {
    + if (skb_copy_bits(skb, BAREUDP_BASE_HLEN, &ipversion,
    + sizeof(ipversion))) {
    + bareudp->dev->stats.rx_dropped++;
    + goto drop;
    + }
    + ipversion >>= 4;
    +
    + if (ipversion == 4) {
    + proto = htons(ETH_P_IP);
    + } else if (ipversion == 6 && bareudp->multi_proto_mode) {
    proto = htons(ETH_P_IPV6);
    } else {
    bareudp->dev->stats.rx_dropped++;
    --
    2.30.2


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