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    Subject[PATCH 3.2 03/94] net: unix: non blocking recvmsg() should not return -EINTR
    3.2.58-rc1 review patch.  If anyone has any objections, please let me know.

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

    From: Eric Dumazet <edumazet@google.com>

    [ Upstream commit de1443916791d75fdd26becb116898277bb0273f ]

    Some applications didn't expect recvmsg() on a non blocking socket
    could return -EINTR. This possibility was added as a side effect
    of commit b3ca9b02b00704 ("net: fix multithreaded signal handling in
    unix recv routines").

    To hit this bug, you need to be a bit unlucky, as the u->readlock
    mutex is usually held for very small periods.

    Fixes: b3ca9b02b00704 ("net: fix multithreaded signal handling in unix recv routines")
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Cc: Rainer Weikusat <rweikusat@mobileactivedefense.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    net/unix/af_unix.c | 17 ++++++++++++-----
    1 file changed, 12 insertions(+), 5 deletions(-)

    --- a/net/unix/af_unix.c
    +++ b/net/unix/af_unix.c
    @@ -1771,8 +1771,11 @@ static int unix_dgram_recvmsg(struct kio
    goto out;

    err = mutex_lock_interruptible(&u->readlock);
    - if (err) {
    - err = sock_intr_errno(sock_rcvtimeo(sk, noblock));
    + if (unlikely(err)) {
    + /* recvmsg() in non blocking mode is supposed to return -EAGAIN
    + * sk_rcvtimeo is not honored by mutex_lock_interruptible()
    + */
    + err = noblock ? -EAGAIN : -ERESTARTSYS;
    goto out;
    }

    @@ -1887,6 +1890,7 @@ static int unix_stream_recvmsg(struct ki
    struct unix_sock *u = unix_sk(sk);
    struct sockaddr_un *sunaddr = msg->msg_name;
    int copied = 0;
    + int noblock = flags & MSG_DONTWAIT;
    int check_creds = 0;
    int target;
    int err = 0;
    @@ -1901,7 +1905,7 @@ static int unix_stream_recvmsg(struct ki
    goto out;

    target = sock_rcvlowat(sk, flags&MSG_WAITALL, size);
    - timeo = sock_rcvtimeo(sk, flags&MSG_DONTWAIT);
    + timeo = sock_rcvtimeo(sk, noblock);

    /* Lock the socket to prevent queue disordering
    * while sleeps in memcpy_tomsg
    @@ -1913,8 +1917,11 @@ static int unix_stream_recvmsg(struct ki
    }

    err = mutex_lock_interruptible(&u->readlock);
    - if (err) {
    - err = sock_intr_errno(timeo);
    + if (unlikely(err)) {
    + /* recvmsg() in non blocking mode is supposed to return -EAGAIN
    + * sk_rcvtimeo is not honored by mutex_lock_interruptible()
    + */
    + err = noblock ? -EAGAIN : -ERESTARTSYS;
    goto out;
    }



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