libtraceevent: Prevent a memory leak in process_fields()

One of the error paths after the field was allocated goes to the wrong
label.  Go to out_free_field if the allocation of arg fails.

Fixes a RESOURCE_LEAK error (CWE-772)

Link: https://lore.kernel.org/linux-trace-devel/20240607160542.46152-3-jmarchan@redhat.com

Fixes: b17b75e511722 ("tools lib traceevent: Handle alloc_arg failure")
Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
1 file changed