• David Sharp's avatar
    ring_buffer: Off-by-one and duplicate events in ring_buffer_read_page · e1e35927
    David Sharp authored
    Fix two related problems in the event-copying loop of
    ring_buffer_read_page.
    
    The loop condition for copying events is off-by-one.
    "len" is the remaining space in the caller-supplied page.
    "size" is the size of the next event (or two events).
    If len == size, then there is just enough space for the next event.
    
    size was set to rb_event_ts_length, which may include the size of two
    events if the first event is a time-extend, in order to assure time-
    extends are kept together with the event after it. However,
    rb_advance_reader always advances by one event. This would result in the
    event after any time-extend being duplicated. Instead, get the size of
    a single event for the memcpy, but use rb_event_ts_length for the loop
    condition.
    Signed-off-by: default avatarDavid Sharp <dhsharp@google.com>
    LKML-Reference: <1293064704-8101-1-git-send-email-dhsharp@google.com>
    LKML-Reference: <AANLkTin7nLrRPc9qGjdjHbeVDDWiJjAiYyb-L=gH85bx@mail.gmail.com>
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    e1e35927
ring_buffer.c 102 KB