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    Subject[PATCH 3.13.y-ckt 137/138] af_unix: Don't set err in unix_stream_read_generic unless there was an error
    Date
    3.13.11-ckt36 -stable review patch.  If anyone has any objections, please let me know.

    ---8<------------------------------------------------------------

    From: Rainer Weikusat <rweikusat@mobileactivedefense.com>

    commit 1b92ee3d03af6643df395300ba7748f19ecdb0c5 upstream.

    The present unix_stream_read_generic contains various code sequences of
    the form

    err = -EDISASTER;
    if (<test>)
    goto out;

    This has the unfortunate side effect of possibly causing the error code
    to bleed through to the final

    out:
    return copied ? : err;

    and then to be wrongly returned if no data was copied because the caller
    didn't supply a data buffer, as demonstrated by the program available at

    http://pad.lv/1540731

    Change it such that err is only set if an error condition was detected.

    Fixes: 3822b5c2fc62 ("af_unix: Revert 'lock_interruptible' in stream receive code")
    Reported-by: Joseph Salisbury <joseph.salisbury@canonical.com>
    Signed-off-by: Rainer Weikusat <rweikusat@mobileactivedefense.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    [ luis: backported to 3.16:
    - modify unix_stream_recvmsg() instead of unix_stream_read_generic()
    - adjusted context ]
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    net/unix/af_unix.c | 16 ++++++++++------
    1 file changed, 10 insertions(+), 6 deletions(-)

    diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
    index 3974413..17a824b 100644
    --- a/net/unix/af_unix.c
    +++ b/net/unix/af_unix.c
    @@ -2089,13 +2089,15 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
    long timeo;
    int skip;

    - err = -EINVAL;
    - if (sk->sk_state != TCP_ESTABLISHED)
    + if (unlikely(sk->sk_state != TCP_ESTABLISHED)) {
    + err = -EINVAL;
    goto out;
    + }

    - err = -EOPNOTSUPP;
    - if (flags&MSG_OOB)
    + if (unlikely(flags & MSG_OOB)) {
    + err = -EOPNOTSUPP;
    goto out;
    + }

    target = sock_rcvlowat(sk, flags&MSG_WAITALL, size);
    timeo = sock_rcvtimeo(sk, noblock);
    @@ -2143,9 +2145,11 @@ again:
    goto unlock;

    unix_state_unlock(sk);
    - err = -EAGAIN;
    - if (!timeo)
    + if (!timeo) {
    + err = -EAGAIN;
    break;
    + }
    +
    mutex_unlock(&u->readlock);

    timeo = unix_stream_data_wait(sk, timeo, last);
    --
    2.7.0
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