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    Subject[PATCH 4.5 025/101] gre: do not pull header in ICMP error processing
    Date
    4.5-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Jiri Benc <jbenc@redhat.com>

    [ Upstream commit b7f8fe251e4609e2a437bd2c2dea01e61db6849c ]

    iptunnel_pull_header expects that IP header was already pulled; with this
    expectation, it pulls the tunnel header. This is not true in gre_err.
    Furthermore, ipv4_update_pmtu and ipv4_redirect expect that skb->data points
    to the IP header.

    We cannot pull the tunnel header in this path. It's just a matter of not
    calling iptunnel_pull_header - we don't need any of its effects.

    Fixes: bda7bb463436 ("gre: Allow multiple protocol listener for gre protocol.")
    Signed-off-by: Jiri Benc <jbenc@redhat.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/ipv4/ip_gre.c | 11 ++++++++---
    1 file changed, 8 insertions(+), 3 deletions(-)

    --- a/net/ipv4/ip_gre.c
    +++ b/net/ipv4/ip_gre.c
    @@ -179,6 +179,7 @@ static __be16 tnl_flags_to_gre_flags(__b
    return flags;
    }

    +/* Fills in tpi and returns header length to be pulled. */
    static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
    bool *csum_err)
    {
    @@ -238,7 +239,7 @@ static int parse_gre_header(struct sk_bu
    return -EINVAL;
    }
    }
    - return iptunnel_pull_header(skb, hdr_len, tpi->proto);
    + return hdr_len;
    }

    static void ipgre_err(struct sk_buff *skb, u32 info,
    @@ -341,7 +342,7 @@ static void gre_err(struct sk_buff *skb,
    struct tnl_ptk_info tpi;
    bool csum_err = false;

    - if (parse_gre_header(skb, &tpi, &csum_err)) {
    + if (parse_gre_header(skb, &tpi, &csum_err) < 0) {
    if (!csum_err) /* ignore csum errors. */
    return;
    }
    @@ -419,6 +420,7 @@ static int gre_rcv(struct sk_buff *skb)
    {
    struct tnl_ptk_info tpi;
    bool csum_err = false;
    + int hdr_len;

    #ifdef CONFIG_NET_IPGRE_BROADCAST
    if (ipv4_is_multicast(ip_hdr(skb)->daddr)) {
    @@ -428,7 +430,10 @@ static int gre_rcv(struct sk_buff *skb)
    }
    #endif

    - if (parse_gre_header(skb, &tpi, &csum_err) < 0)
    + hdr_len = parse_gre_header(skb, &tpi, &csum_err);
    + if (hdr_len < 0)
    + goto drop;
    + if (iptunnel_pull_header(skb, hdr_len, tpi.proto) < 0)
    goto drop;

    if (ipgre_rcv(skb, &tpi) == PACKET_RCVD)

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