• Jeff Layton's avatar
    locks: fix unlock when fcntl_setlk races with a close · 993e1630
    Jeff Layton authored
    commit 7f3697e2 upstream.
    
    Dmitry reported that he was able to reproduce the WARN_ON_ONCE that
    fires in locks_free_lock_context when the flc_posix list isn't empty.
    
    The problem turns out to be that we're basically rebuilding the
    file_lock from scratch in fcntl_setlk when we discover that the setlk
    has raced with a close. If the l_whence field is SEEK_CUR or SEEK_END,
    then we may end up with fl_start and fl_end values that differ from
    when the lock was initially set, if the file position or length of the
    file has changed in the interim.
    
    Fix this by just reusing the same lock request structure, and simply
    override fl_type value with F_UNLCK as appropriate. That ensures that
    we really are unlocking the lock that was initially set.
    
    While we're there, make sure that we do pop a WARN_ON_ONCE if the
    removal ever fails. Also return -EBADF in this event, since that's
    what we would have returned if the close had happened earlier.
    
    Cc: Alexander Viro <viro@zeniv.linux.org.uk>
    Fixes: c293621b (stale POSIX lock handling)
    Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
    Signed-off-by: default avatarJeff Layton <jeff.layton@primarydata.com>
    Acked-by: default avatar"J. Bruce Fields" <bfields@fieldses.org>
    Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
    993e1630
locks.c 69.3 KB