perf daemon: Fix compile error with Asan

I'm seeing a build failure when build with address sanitizer.  It seems
we could write to the name[100] if the var is longer.

  $ make EXTRA_CFLAGS=-fsanitize=address
  ...
    CC       builtin-daemon.o
  In function ‘get_session_name’,
    inlined from ‘session_config’ at builtin-daemon.c:164:6,
    inlined from ‘server_config’ at builtin-daemon.c:223:10:
  builtin-daemon.c:155:11: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=]
    155 |  *session = 0;
        |  ~~~~~~~~~^~~
  builtin-daemon.c: In function ‘server_config’:
  builtin-daemon.c:162:7: note: at offset 100 to object ‘name’ with size 100 declared here
    162 |  char name[100];
        |       ^~~~

Fixes: c0666261ff ("perf daemon: Add config file support")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20210224071438.686677-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-daemon.c

@@ -161,7 +161,7 @@ static int session_config(struct daemon *daemon, const char *var, const char *va
 	struct daemon_session *session;
 	char name[100];
 
-	if (get_session_name(var, name, sizeof(name)))
+	if (get_session_name(var, name, sizeof(name) - 1))
 		return -EINVAL;
 
 	var = strchr(var, '.');