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    Subject[PATCH] tracing: Add size check when printing trace_marker output
    From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

    If for some reason the trace_marker write does not have a nul byte for the
    string, it will overflow the print:

    trace_seq_printf(s, ": %s", field->buf);

    The field->buf could be missing the nul byte. To prevent overflow, add the
    max size that the buf can be by using the event size and the field
    location.

    int max = iter->ent_size - offsetof(struct print_entry, buf);

    trace_seq_printf(s, ": %*s", max, field->buf);

    Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
    ---
    kernel/trace/trace_output.c | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
    index d8b302d01083..e11fb8996286 100644
    --- a/kernel/trace/trace_output.c
    +++ b/kernel/trace/trace_output.c
    @@ -1587,11 +1587,12 @@ static enum print_line_t trace_print_print(struct trace_iterator *iter,
    {
    struct print_entry *field;
    struct trace_seq *s = &iter->seq;
    + int max = iter->ent_size - offsetof(struct print_entry, buf);

    trace_assign_type(field, iter->ent);

    seq_print_ip_sym(s, field->ip, flags);
    - trace_seq_printf(s, ": %s", field->buf);
    + trace_seq_printf(s, ": %*s", max, field->buf);

    return trace_handle_return(s);
    }
    @@ -1600,10 +1601,11 @@ static enum print_line_t trace_print_raw(struct trace_iterator *iter, int flags,
    struct trace_event *event)
    {
    struct print_entry *field;
    + int max = iter->ent_size - offsetof(struct print_entry, buf);

    trace_assign_type(field, iter->ent);

    - trace_seq_printf(&iter->seq, "# %lx %s", field->ip, field->buf);
    + trace_seq_printf(&iter->seq, "# %lx %*s", field->ip, max, field->buf);

    return trace_handle_return(&iter->seq);
    }
    --
    2.42.0
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