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    Subject[PATCH 3.10 06/31] ipmr: fix possible race resulting from improper usage of IP_INC_STATS_BH() in preemptible context.
    Date
    3.10-stable review patch.  If anyone has any objections, please let me know.

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

    From: Ani Sinha <ani@arista.com>

    [ Upstream commit 44f49dd8b5a606870a1f21101522a0f9c4414784 ]

    Fixes the following kernel BUG :

    BUG: using __this_cpu_add() in preemptible [00000000] code: bash/2758
    caller is __this_cpu_preempt_check+0x13/0x15
    CPU: 0 PID: 2758 Comm: bash Tainted: P O 3.18.19 #2
    ffffffff8170eaca ffff880110d1b788 ffffffff81482b2a 0000000000000000
    0000000000000000 ffff880110d1b7b8 ffffffff812010ae ffff880007cab800
    ffff88001a060800 ffff88013a899108 ffff880108b84240 ffff880110d1b7c8
    Call Trace:
    [<ffffffff81482b2a>] dump_stack+0x52/0x80
    [<ffffffff812010ae>] check_preemption_disabled+0xce/0xe1
    [<ffffffff812010d4>] __this_cpu_preempt_check+0x13/0x15
    [<ffffffff81419d60>] ipmr_queue_xmit+0x647/0x70c
    [<ffffffff8141a154>] ip_mr_forward+0x32f/0x34e
    [<ffffffff8141af76>] ip_mroute_setsockopt+0xe03/0x108c
    [<ffffffff810553fc>] ? get_parent_ip+0x11/0x42
    [<ffffffff810e6974>] ? pollwake+0x4d/0x51
    [<ffffffff81058ac0>] ? default_wake_function+0x0/0xf
    [<ffffffff810553fc>] ? get_parent_ip+0x11/0x42
    [<ffffffff810613d9>] ? __wake_up_common+0x45/0x77
    [<ffffffff81486ea9>] ? _raw_spin_unlock_irqrestore+0x1d/0x32
    [<ffffffff810618bc>] ? __wake_up_sync_key+0x4a/0x53
    [<ffffffff8139a519>] ? sock_def_readable+0x71/0x75
    [<ffffffff813dd226>] do_ip_setsockopt+0x9d/0xb55
    [<ffffffff81429818>] ? unix_seqpacket_sendmsg+0x3f/0x41
    [<ffffffff813963fe>] ? sock_sendmsg+0x6d/0x86
    [<ffffffff813959d4>] ? sockfd_lookup_light+0x12/0x5d
    [<ffffffff8139650a>] ? SyS_sendto+0xf3/0x11b
    [<ffffffff810d5738>] ? new_sync_read+0x82/0xaa
    [<ffffffff813ddd19>] compat_ip_setsockopt+0x3b/0x99
    [<ffffffff813fb24a>] compat_raw_setsockopt+0x11/0x32
    [<ffffffff81399052>] compat_sock_common_setsockopt+0x18/0x1f
    [<ffffffff813c4d05>] compat_SyS_setsockopt+0x1a9/0x1cf
    [<ffffffff813c4149>] compat_SyS_socketcall+0x180/0x1e3
    [<ffffffff81488ea1>] cstar_dispatch+0x7/0x1e

    Signed-off-by: Ani Sinha <ani@arista.com>
    Acked-by: Eric Dumazet <edumazet@google.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/ipv4/ipmr.c | 6 +++---
    1 file changed, 3 insertions(+), 3 deletions(-)

    --- a/net/ipv4/ipmr.c
    +++ b/net/ipv4/ipmr.c
    @@ -1672,8 +1672,8 @@ static inline int ipmr_forward_finish(st
    {
    struct ip_options *opt = &(IPCB(skb)->opt);

    - IP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTFORWDATAGRAMS);
    - IP_ADD_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTOCTETS, skb->len);
    + IP_INC_STATS(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTFORWDATAGRAMS);
    + IP_ADD_STATS(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTOCTETS, skb->len);

    if (unlikely(opt->optlen))
    ip_forward_options(skb);
    @@ -1735,7 +1735,7 @@ static void ipmr_queue_xmit(struct net *
    * to blackhole.
    */

    - IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
    + IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
    ip_rt_put(rt);
    goto out_free;
    }



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