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    Subject[PATCH 5.15 551/667] tracing: Fix potential double free in create_var_ref()
    Date
    From: Keita Suzuki <keitasuzuki.park@sslab.ics.keio.ac.jp>

    commit 99696a2592bca641eb88cc9a80c90e591afebd0f upstream.

    In create_var_ref(), init_var_ref() is called to initialize the fields
    of variable ref_field, which is allocated in the previous function call
    to create_hist_field(). Function init_var_ref() allocates the
    corresponding fields such as ref_field->system, but frees these fields
    when the function encounters an error. The caller later calls
    destroy_hist_field() to conduct error handling, which frees the fields
    and the variable itself. This results in double free of the fields which
    are already freed in the previous function.

    Fix this by storing NULL to the corresponding fields when they are freed
    in init_var_ref().

    Link: https://lkml.kernel.org/r/20220425063739.3859998-1-keitasuzuki.park@sslab.ics.keio.ac.jp

    Fixes: 067fe038e70f ("tracing: Add variable reference handling to hist triggers")
    CC: stable@vger.kernel.org
    Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
    Reviewed-by: Tom Zanussi <zanussi@kernel.org>
    Signed-off-by: Keita Suzuki <keitasuzuki.park@sslab.ics.keio.ac.jp>
    Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    kernel/trace/trace_events_hist.c | 3 +++
    1 file changed, 3 insertions(+)

    --- a/kernel/trace/trace_events_hist.c
    +++ b/kernel/trace/trace_events_hist.c
    @@ -1838,8 +1838,11 @@ static int init_var_ref(struct hist_fiel
    return err;
    free:
    kfree(ref_field->system);
    + ref_field->system = NULL;
    kfree(ref_field->event_name);
    + ref_field->event_name = NULL;
    kfree(ref_field->name);
    + ref_field->name = NULL;

    goto out;
    }

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