releases/4.16.17/bpf-fix-uninitialized-variable-in-bpf-tools.patch

From foo@baz Sun Jun 17 12:07:33 CEST 2018
From: John Fastabend <john.fastabend@gmail.com>
Date: Wed, 25 Apr 2018 15:08:53 -0700
Subject: bpf: fix uninitialized variable in bpf tools

From: John Fastabend <john.fastabend@gmail.com>

[ Upstream commit 815425567dea6c54494e85050631d6bdda907c5d ]

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: fd981e3c321a "filter: bpf_dbg: add minimal bpf debugger"
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 tools/bpf/bpf_dbg.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- 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 {