tracing/probes: Fix to avoid double count of the string length on the array

tracing/probes: Fix to avoid double count of the string length on the array

[ Upstream commit 66bcf65d6cf0ca6540e2341e88ee7ef02dbdda08 ]

If an array is specified with the ustring or symstr, the length of the
strings are accumlated on both of 'ret' and 'total', which means the
length is double counted.
Just set the length to the 'ret' value for avoiding double counting.

Link: https://lore.kernel.org/all/168908492917.123124.15076463491122036025.stgit@devnote2/
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/all/8819b154-2ba1-43c3-98a2-cbde20892023@moroto.mountain/
Fixes: 88903c464321 ("tracing/probe: Add ustring type for user-space string")
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>