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    Subject[PATCH 139/270] libceph: avoid dropping con mutex before fault
    Date
    3.5.7u1 -stable review patch.  If anyone has any objections, please let me know.

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

    From: Sage Weil <sage@inktank.com>

    commit 8636ea672f0c5ab7478c42c5b6705ebd1db7eb6a upstream.

    The ceph_fault() function takes the con mutex, so we should avoid
    dropping it before calling it. This fixes a potential race with
    another thread calling ceph_con_close(), or _open(), or similar (we
    don't reverify con->state after retaking the lock).

    Add annotation so that lockdep realizes we will drop the mutex before
    returning.

    Signed-off-by: Sage Weil <sage@inktank.com>
    Reviewed-by: Alex Elder <elder@inktank.com>
    Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
    ---
    net/ceph/messenger.c | 4 +---
    1 file changed, 1 insertion(+), 3 deletions(-)

    diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
    index feb5a2a..c3b628c 100644
    --- a/net/ceph/messenger.c
    +++ b/net/ceph/messenger.c
    @@ -2336,7 +2336,6 @@ done_unlocked:
    return;

    fault:
    - mutex_unlock(&con->mutex);
    ceph_fault(con); /* error/fault path */
    goto done_unlocked;
    }
    @@ -2347,9 +2346,8 @@ fault:
    * exponential backoff
    */
    static void ceph_fault(struct ceph_connection *con)
    + __releases(con->mutex)
    {
    - mutex_lock(&con->mutex);
    -
    pr_err("%s%lld %s %s\n", ENTITY_NAME(con->peer_name),
    ceph_pr_addr(&con->peer_addr.in_addr), con->error_msg);
    dout("fault %p state %lu to peer %s\n",
    --
    1.7.9.5


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