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    Subject[PATCH 5.15 021/244] tracing/eprobes: Do not hardcode $comm as a string
    Date
    From: Steven Rostedt (Google) <rostedt@goodmis.org>

    commit 02333de90e5945e2fe7fc75b15b4eb9aee187f0a upstream.

    The variable $comm is hard coded as a string, which is true for both
    kprobes and uprobes, but for event probes (eprobes) it is a field name. In
    most cases the "comm" field would be a string, but there's no guarantee of
    that fact.

    Do not assume that comm is a string. Not to mention, it currently forces
    comm fields to fault, as string processing for event probes is currently
    broken.

    Link: https://lkml.kernel.org/r/20220820134400.756152112@goodmis.org

    Cc: stable@vger.kernel.org
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Masami Hiramatsu <mhiramat@kernel.org>
    Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
    Cc: Tom Zanussi <zanussi@kernel.org>
    Fixes: 7491e2c44278 ("tracing: Add a probe that attaches to trace events")
    Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    kernel/trace/trace_probe.c | 5 +++--
    1 file changed, 3 insertions(+), 2 deletions(-)

    --- a/kernel/trace/trace_probe.c
    +++ b/kernel/trace/trace_probe.c
    @@ -618,9 +618,10 @@ static int traceprobe_parse_probe_arg_bo

    /*
    * Since $comm and immediate string can not be dereferenced,
    - * we can find those by strcmp.
    + * we can find those by strcmp. But ignore for eprobes.
    */
    - if (strcmp(arg, "$comm") == 0 || strncmp(arg, "\\\"", 2) == 0) {
    + if (!(flags & TPARG_FL_TPOINT) &&
    + (strcmp(arg, "$comm") == 0 || strncmp(arg, "\\\"", 2) == 0)) {
    /* The type of $comm must be "string", and not an array. */
    if (parg->count || (t && strcmp(t, "string")))
    goto out;

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