lkml.org 
[lkml]   [2010]   [Oct]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[42/66] tcp: Fix race in tcp_poll
    2.6.32-stable review patch.  If anyone has any objections, please let us know.

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


    From: Tom Marshall <tdm.code@gmail.com>

    [ Upstream commit a4d258036ed9b2a1811c3670c6099203a0f284a0 ]

    If a RST comes in immediately after checking sk->sk_err, tcp_poll will
    return POLLIN but not POLLOUT. Fix this by checking sk->sk_err at the end
    of tcp_poll. Additionally, ensure the correct order of operations on SMP
    machines with memory barriers.

    Signed-off-by: Tom Marshall <tdm.code@gmail.com>
    Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    ---
    net/ipv4/tcp.c | 7 +++++--
    net/ipv4/tcp_input.c | 2 ++
    2 files changed, 7 insertions(+), 2 deletions(-)

    --- a/net/ipv4/tcp.c
    +++ b/net/ipv4/tcp.c
    @@ -386,8 +386,6 @@ unsigned int tcp_poll(struct file *file,
    */

    mask = 0;
    - if (sk->sk_err)
    - mask = POLLERR;

    /*
    * POLLHUP is certainly not done right. But poll() doesn't
    @@ -457,6 +455,11 @@ unsigned int tcp_poll(struct file *file,
    if (tp->urg_data & TCP_URG_VALID)
    mask |= POLLPRI;
    }
    + /* This barrier is coupled with smp_wmb() in tcp_reset() */
    + smp_rmb();
    + if (sk->sk_err)
    + mask |= POLLERR;
    +
    return mask;
    }

    --- a/net/ipv4/tcp_input.c
    +++ b/net/ipv4/tcp_input.c
    @@ -3969,6 +3969,8 @@ static void tcp_reset(struct sock *sk)
    default:
    sk->sk_err = ECONNRESET;
    }
    + /* This barrier is coupled with smp_rmb() in tcp_poll() */
    + smp_wmb();

    if (!sock_flag(sk, SOCK_DEAD))
    sk->sk_error_report(sk);



    \
     
     \ /
      Last update: 2010-10-22 20:51    [W:4.131 / U:0.260 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site