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    Subject[PATCH 4.19 228/422] ip_gre: fix parsing gre header in ipgre_err
    Date
    From: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>

    [ Upstream commit b0350d51f001e6edc13ee4f253b98b50b05dd401 ]

    gre_parse_header stops parsing when csum_err is encountered, which means
    tpi->key is undefined and ip_tunnel_lookup will return NULL improperly.

    This patch introduce a NULL pointer as csum_err parameter. Even when
    csum_err is encountered, it won't return error and continue parsing gre
    header as expected.

    Fixes: 9f57c67c379d ("gre: Remove support for sharing GRE protocol hook.")
    Reported-by: Jiri Benc <jbenc@redhat.com>
    Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/ipv4/gre_demux.c | 7 ++++---
    net/ipv4/ip_gre.c | 9 +++------
    2 files changed, 7 insertions(+), 9 deletions(-)

    diff --git a/net/ipv4/gre_demux.c b/net/ipv4/gre_demux.c
    index f21ea6125fc2d..511b32ea25331 100644
    --- a/net/ipv4/gre_demux.c
    +++ b/net/ipv4/gre_demux.c
    @@ -87,13 +87,14 @@ int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,

    options = (__be32 *)(greh + 1);
    if (greh->flags & GRE_CSUM) {
    - if (skb_checksum_simple_validate(skb)) {
    + if (!skb_checksum_simple_validate(skb)) {
    + skb_checksum_try_convert(skb, IPPROTO_GRE, 0,
    + null_compute_pseudo);
    + } else if (csum_err) {
    *csum_err = true;
    return -EINVAL;
    }

    - skb_checksum_try_convert(skb, IPPROTO_GRE, 0,
    - null_compute_pseudo);
    options++;
    }

    diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
    index 758a0f86d499f..681276111310b 100644
    --- a/net/ipv4/ip_gre.c
    +++ b/net/ipv4/ip_gre.c
    @@ -232,13 +232,10 @@ static void gre_err(struct sk_buff *skb, u32 info)
    const int type = icmp_hdr(skb)->type;
    const int code = icmp_hdr(skb)->code;
    struct tnl_ptk_info tpi;
    - bool csum_err = false;

    - if (gre_parse_header(skb, &tpi, &csum_err, htons(ETH_P_IP),
    - iph->ihl * 4) < 0) {
    - if (!csum_err) /* ignore csum errors. */
    - return;
    - }
    + if (gre_parse_header(skb, &tpi, NULL, htons(ETH_P_IP),
    + iph->ihl * 4) < 0)
    + return;

    if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
    ipv4_update_pmtu(skb, dev_net(skb->dev), info,
    --
    2.20.1


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