lkml.org 
[lkml]   [2011]   [Jul]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH] [93/99] ipv6/udp: Use the correct variable to determine non-blocking condition
    Date
    2.6.35-longterm review patch.  If anyone has any objections, please let me know.

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

    From: Xufeng Zhang <xufeng.zhang@windriver.com>

    [ Upstream commit 32c90254ed4a0c698caa0794ebb4de63fcc69631 ]

    udpv6_recvmsg() function is not using the correct variable to determine
    whether or not the socket is in non-blocking operation, this will lead
    to unexpected behavior when a UDP checksum error occurs.

    Consider a non-blocking udp receive scenario: when udpv6_recvmsg() is
    called by sock_common_recvmsg(), MSG_DONTWAIT bit of flags variable in
    udpv6_recvmsg() is cleared by "flags & ~MSG_DONTWAIT" in this call:

    err = sk->sk_prot->recvmsg(iocb, sk, msg, size, flags & MSG_DONTWAIT,
    flags & ~MSG_DONTWAIT, &addr_len);

    i.e. with udpv6_recvmsg() getting these values:

    int noblock = flags & MSG_DONTWAIT
    int flags = flags & ~MSG_DONTWAIT

    So, when udp checksum error occurs, the execution will go to
    csum_copy_err, and then the problem happens:

    csum_copy_err:
    ...............
    if (flags & MSG_DONTWAIT)
    return -EAGAIN;
    goto try_again;
    ...............

    But it will always go to try_again as MSG_DONTWAIT has been cleared
    from flags at call time -- only noblock contains the original value
    of MSG_DONTWAIT, so the test should be:

    if (noblock)
    return -EAGAIN;

    This is also consistent with what the ipv4/udp code does.

    Signed-off-by: Xufeng Zhang <xufeng.zhang@windriver.com>
    Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    Signed-off-by: Andi Kleen <ak@linux.intel.com>

    ---
    net/ipv6/udp.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    Index: linux-2.6.35.y/net/ipv6/udp.c
    ===================================================================
    --- linux-2.6.35.y.orig/net/ipv6/udp.c
    +++ linux-2.6.35.y/net/ipv6/udp.c
    @@ -445,7 +445,7 @@ csum_copy_err:
    }
    unlock_sock_fast(sk, slow);

    - if (flags & MSG_DONTWAIT)
    + if (noblock)
    return -EAGAIN;
    goto try_again;
    }

    \
     
     \ /
      Last update: 2011-07-27 23:55    [W:0.022 / U:29.668 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site