tracing/eprobes: Do not hardcode $comm as a string

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>

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 61ab7fc..fb54564 100644 (file)
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -618,9 +618,10 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size,
 
        /*
         * 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;