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    Subject[PATCH 124/270] libceph: (re)initialize bio_iter on start of message receive
    Date
    3.5.7u1 -stable review patch.  If anyone has any objections, please let me know.

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

    From: Sage Weil <sage@inktank.com>

    commit a4107026976f06c9a6ce8cc84a763564ee39d901 upstream.

    Previously, we were opportunistically initializing the bio_iter if it
    appeared to be uninitialized in the middle of the read path. The problem
    is that a sequence like:

    - start reading message
    - initialize bio_iter
    - read half a message
    - messenger fault, reconnect
    - restart reading message
    - ** bio_iter now non-NULL, not reinitialized **
    - read past end of bio, crash

    Instead, initialize the bio_iter unconditionally when we allocate/claim
    the message for read.

    Signed-off-by: Sage Weil <sage@inktank.com>
    Reviewed-by: Alex Elder <elder@inktank.com>
    Reviewed-by: Yehuda Sadeh <yehuda@inktank.com>
    Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
    ---
    net/ceph/messenger.c | 11 ++++++-----
    1 file changed, 6 insertions(+), 5 deletions(-)

    diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
    index e65b15d..f1bd3bb 100644
    --- a/net/ceph/messenger.c
    +++ b/net/ceph/messenger.c
    @@ -1872,6 +1872,11 @@ static int read_partial_message(struct ceph_connection *con)
    else
    con->in_msg_pos.page_pos = 0;
    con->in_msg_pos.data_pos = 0;
    +
    +#ifdef CONFIG_BLOCK
    + if (m->bio)
    + init_bio_iter(m->bio, &m->bio_iter, &m->bio_seg);
    +#endif
    }

    /* front */
    @@ -1888,10 +1893,6 @@ static int read_partial_message(struct ceph_connection *con)
    if (ret <= 0)
    return ret;
    }
    -#ifdef CONFIG_BLOCK
    - if (m->bio && !m->bio_iter)
    - init_bio_iter(m->bio, &m->bio_iter, &m->bio_seg);
    -#endif

    /* (page) data */
    while (con->in_msg_pos.data_pos < data_len) {
    @@ -1902,7 +1903,7 @@ static int read_partial_message(struct ceph_connection *con)
    return ret;
    #ifdef CONFIG_BLOCK
    } else if (m->bio) {
    -
    + BUG_ON(!m->bio_iter);
    ret = read_partial_message_bio(con,
    &m->bio_iter, &m->bio_seg,
    data_len, do_datacrc);
    --
    1.7.9.5


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