From a33f669662b9a96da36c48b703eb5672209249d0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pali=20Roh=C3=A1r?= <pali@kernel.org>
Date: Sat, 7 Aug 2021 15:27:03 +0200
Subject: [PATCH 3/7] ppp: Fix generating ifname when empty IFLA_IFNAME is
specified
Git-commit: 2459dcb96bcba94c08d6861f8a050185ff301672
Patch-mainline: v5.14-rc6
References: git-fixes
IFLA_IFNAME is nul-term string which means that IFLA_IFNAME buffer can be
larger than length of string which contains.
Function __rtnl_newlink() generates new own ifname if either IFLA_IFNAME
was not specified at all or userspace passed empty nul-term string.
It is expected that if userspace does not specify ifname for new ppp netdev
then kernel generates one in format "ppp<id>" where id matches to the ppp
unit id which can be later obtained by PPPIOCGUNIT ioctl.
And it works in this way if IFLA_IFNAME is not specified at all. But it
does not work when IFLA_IFNAME is specified with empty string.
So fix this logic also for empty IFLA_IFNAME in ppp_nl_newlink() function
and correctly generates ifname based on ppp unit identifier if userspace
did not provided preferred ifname.
Without this patch when IFLA_IFNAME was specified with empty string then
kernel created a new ppp interface in format "ppp<id>" but id did not
match ppp unit id returned by PPPIOCGUNIT ioctl. In this case id was some
number generated by __rtnl_newlink() function.
Signed-off-by: Pali Rohár <pali@kernel.org>
Fixes: bb8082f69138 ("ppp: build ifname using unit identifier for rtnl based devices")
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Denis Kirjanov <denis.kirjanov@suse.com>
---
drivers/net/ppp/ppp_generic.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index 352e751125fb..56b0bd90a9fb 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -1116,7 +1116,7 @@ static int ppp_nl_newlink(struct net *src_net, struct net_device *dev,
* the PPP unit identifer as suffix (i.e. ppp<unit_id>). This allows
* userspace to infer the device name using to the PPPIOCGUNIT ioctl.
*/
- if (!tb[IFLA_IFNAME])
+ if (!tb[IFLA_IFNAME] || !nla_len(tb[IFLA_IFNAME]) || !*(char *)nla_data(tb[IFLA_IFNAME]))
conf.ifname_is_set = false;
err = ppp_dev_configure(src_net, dev, &conf);
--
2.16.4