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    Subject[PATCH 5.4 16/49] gtp: fix an use-before-init in gtp_newlink()
    Date
    From: Masahiro Fujiwara <fujiwara.masahiro@gmail.com>

    [ Upstream commit 51467431200b91682b89d31317e35dcbca1469ce ]

    *_pdp_find() from gtp_encap_recv() would trigger a crash when a peer
    sends GTP packets while creating new GTP device.

    RIP: 0010:gtp1_pdp_find.isra.0+0x68/0x90 [gtp]
    <SNIP>
    Call Trace:
    <IRQ>
    gtp_encap_recv+0xc2/0x2e0 [gtp]
    ? gtp1_pdp_find.isra.0+0x90/0x90 [gtp]
    udp_queue_rcv_one_skb+0x1fe/0x530
    udp_queue_rcv_skb+0x40/0x1b0
    udp_unicast_rcv_skb.isra.0+0x78/0x90
    __udp4_lib_rcv+0x5af/0xc70
    udp_rcv+0x1a/0x20
    ip_protocol_deliver_rcu+0xc5/0x1b0
    ip_local_deliver_finish+0x48/0x50
    ip_local_deliver+0xe5/0xf0
    ? ip_protocol_deliver_rcu+0x1b0/0x1b0

    gtp_encap_enable() should be called after gtp_hastable_new() otherwise
    *_pdp_find() will access the uninitialized hash table.

    Fixes: 1e3a3abd8b28 ("gtp: make GTP sockets in gtp_newlink optional")
    Signed-off-by: Masahiro Fujiwara <fujiwara.masahiro@gmail.com>
    Link: https://lore.kernel.org/r/20201027114846.3924-1-fujiwara.masahiro@gmail.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/net/gtp.c | 16 ++++++++--------
    1 file changed, 8 insertions(+), 8 deletions(-)

    --- a/drivers/net/gtp.c
    +++ b/drivers/net/gtp.c
    @@ -663,10 +663,6 @@ static int gtp_newlink(struct net *src_n

    gtp = netdev_priv(dev);

    - err = gtp_encap_enable(gtp, data);
    - if (err < 0)
    - return err;
    -
    if (!data[IFLA_GTP_PDP_HASHSIZE]) {
    hashsize = 1024;
    } else {
    @@ -677,12 +673,16 @@ static int gtp_newlink(struct net *src_n

    err = gtp_hashtable_new(gtp, hashsize);
    if (err < 0)
    - goto out_encap;
    + return err;
    +
    + err = gtp_encap_enable(gtp, data);
    + if (err < 0)
    + goto out_hashtable;

    err = register_netdevice(dev);
    if (err < 0) {
    netdev_dbg(dev, "failed to register new netdev %d\n", err);
    - goto out_hashtable;
    + goto out_encap;
    }

    gn = net_generic(dev_net(dev), gtp_net_id);
    @@ -693,11 +693,11 @@ static int gtp_newlink(struct net *src_n

    return 0;

    +out_encap:
    + gtp_encap_disable(gtp);
    out_hashtable:
    kfree(gtp->addr_hash);
    kfree(gtp->tid_hash);
    -out_encap:
    - gtp_encap_disable(gtp);
    return err;
    }


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