samples: bpf: fix: seg fault with NULL pointer arg

DanielTimLee · borkmann · commit d59dd69d5576 · 2018-12-03T23:58:03.000+01:00
When NULL pointer accidentally passed to write_kprobe_events,
due to strlen(NULL), segmentation fault happens.
Changed code returns -1 to deal with this situation.

Bug issued with Smatch, static analysis.

Signed-off-by: Daniel T. Lee &lt;danieltimlee@gmail.com&gt;
Acked-by: Song Liu &lt;songliubraving@fb.com&gt;
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c
@@ -58,7 +58,9 @@ static int write_kprobe_events(const char *val)
 {
 	int fd, ret, flags;
 
-	if ((val != NULL) && (val[0] == '\0'))
+	if (val == NULL)
+		return -1;
+	else if (val[0] == '\0')
 		flags = O_WRONLY | O_TRUNC;
 	else
 		flags = O_WRONLY | O_APPEND;
