bpf: fix uninitialized variable in bpf tools

jrfastab · borkmann · commit 815425567dea · 2018-04-26T22:23:02.000+02:00
Here the variable cont is used as the saved_pointer for a call to strtok_r(). It is safe to use the value uninitialized in this context however and the later reference is only ever used if the strtok_r is successful. But, 'gcc-5' at least doesn't have all this knowledge so initialize cont to NULL. Additionally, do the natural NULL check before accessing just for completness. The warning is the following: ./bpf/tools/bpf/bpf_dbg.c: In function ‘cmd_load’: ./bpf/tools/bpf/bpf_dbg.c:1077:13: warning: ‘cont’ may be used uninitialized in this function [-Wmaybe-uninitialized] } else if (matches(subcmd, "pcap") == 0) { Fixes: fd981e3 "filter: bpf_dbg: add minimal bpf debugger" Signed-off-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
diff --git a/tools/bpf/bpf_dbg.c b/tools/bpf/bpf_dbg.c
@@ -1063,7 +1063,7 @@ static int cmd_load_pcap(char *file)
 
 static int cmd_load(char *arg)
 {
-	char *subcmd, *cont, *tmp = strdup(arg);
+	char *subcmd, *cont = NULL, *tmp = strdup(arg);
 	int ret = CMD_OK;
 
 	subcmd = strtok_r(tmp, " ", &cont);
@@ -1073,7 +1073,10 @@ static int cmd_load(char *arg)
 		bpf_reset();
 		bpf_reset_breakpoints();
 
-		ret = cmd_load_bpf(cont);
+		if (!cont)
+			ret = CMD_ERR;
+		else
+			ret = cmd_load_bpf(cont);
 	} else if (matches(subcmd, "pcap") == 0) {
 		ret = cmd_load_pcap(cont);
 	} else {
