[PATCH v4 2/4] tracing/probes: Fix not to count error code to total length

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Fix not to count the error code (which is minus value) to the total
used length of array, because it can mess up the return code of
process_fetch_insn_bottom(). Also clear the 'ret' value because it
will be used for calculating next data_loc entry.

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/all/8819b154-2ba1-43c3-98a2-cbde20892023@moroto.mountain/
Fixes: 9b960a38835f ("tracing: probeevent: Unify fetch_insn processing common part")
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
Changes in v2:
 - Check and clear ret only for the array argument.
---
 kernel/trace/trace_probe_tmpl.h |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/trace/trace_probe_tmpl.h b/kernel/trace/trace_probe_tmpl.h
index 4735c5cb76fa..ed9d57c6b041 100644
--- a/kernel/trace/trace_probe_tmpl.h
+++ b/kernel/trace/trace_probe_tmpl.h
@@ -204,6 +204,8 @@ process_fetch_insn_bottom(struct fetch_insn *code, unsigned long val,
 array:
 	/* the last stage: Loop on array */
 	if (code->op == FETCH_OP_LP_ARRAY) {
+		if (ret < 0)
+			ret = 0;
 		total += ret;
 		if (++i < code->param) {
 			code = s3;