diff mbox series

[3/3] batman-adv: Don't expect inter-netns unique iflink indices

Message ID 20220302163049.101957-4-sw@simonwunderlich.de (mailing list archive)
State Accepted
Commit 6c1f41afc1dbe59d9d3c8bb0d80b749c119aa334
Delegated to: Netdev Maintainers
Headers show
Series [1/3] batman-adv: Request iflink once in batadv-on-batadv check | expand

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Context Check Description
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix warning Target tree name not specified in the subject
netdev/cover_letter success Pull request is its own cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers fail 2 blamed authors not CCed: mareklindner@neomailbox.ch a@unstable.cc; 2 maintainers not CCed: a@unstable.cc mareklindner@neomailbox.ch
netdev/build_clang success Errors and warnings before: 0 this patch: 0
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 41 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/tree_selection success Guessing tree name failed - patch did not apply

Commit Message

Simon Wunderlich March 2, 2022, 4:30 p.m. UTC 
From: Sven Eckelmann <sven@narfation.org>

The ifindex doesn't have to be unique for multiple network namespaces on
the same machine.

  $ ip netns add test1
  $ ip -net test1 link add dummy1 type dummy
  $ ip netns add test2
  $ ip -net test2 link add dummy2 type dummy

  $ ip -net test1 link show dev dummy1
  6: dummy1: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
      link/ether 96:81:55:1e:dd:85 brd ff:ff:ff:ff:ff:ff
  $ ip -net test2 link show dev dummy2
  6: dummy2: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
      link/ether 5a:3c:af:35:07:c3 brd ff:ff:ff:ff:ff:ff

But the batman-adv code to walk through the various layers of virtual
interfaces uses this assumption because dev_get_iflink handles it
internally and doesn't return the actual netns of the iflink. And
dev_get_iflink only documents the situation where ifindex == iflink for
physical devices.

But only checking for dev->netdev_ops->ndo_get_iflink is also not an option
because ipoib_get_iflink implements it even when it sometimes returns an
iflink != ifindex and sometimes iflink == ifindex. The caller must
therefore make sure itself to check both netns and iflink + ifindex for
equality. Only when they are equal, a "physical" interface was detected
which should stop the traversal. On the other hand, vxcan_get_iflink can
also return 0 in case there was currently no valid peer. In this case, it
is still necessary to stop.

Fixes: b7eddd0b3950 ("batman-adv: prevent using any virtual device created on batman-adv as hard-interface")
Fixes: 5ed4a460a1d3 ("batman-adv: additional checks for virtual interfaces on top of WiFi")
Reported-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
---
 net/batman-adv/hard-interface.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)
diff mbox series

Patch

diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index e2760cfce190..35fadb924849 100644
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -157,13 +157,15 @@  static bool batadv_is_on_batman_iface(const struct net_device *net_dev)
 		return true;
 
 	iflink = dev_get_iflink(net_dev);
-
-	/* no more parents..stop recursion */
-	if (iflink == 0 || iflink == net_dev->ifindex)
+	if (iflink == 0)
 		return false;
 
 	parent_net = batadv_getlink_net(net_dev, net);
 
+	/* iflink to itself, most likely physical device */
+	if (net == parent_net && iflink == net_dev->ifindex)
+		return false;
+
 	/* recurse over the parent device */
 	parent_dev = __dev_get_by_index((struct net *)parent_net, iflink);
 	/* if we got a NULL parent_dev there is something broken.. */
@@ -223,8 +225,7 @@  static struct net_device *batadv_get_real_netdevice(struct net_device *netdev)
 		return NULL;
 
 	iflink = dev_get_iflink(netdev);
-
-	if (netdev->ifindex == iflink) {
+	if (iflink == 0) {
 		dev_hold(netdev);
 		return netdev;
 	}
@@ -235,6 +236,14 @@  static struct net_device *batadv_get_real_netdevice(struct net_device *netdev)
 
 	net = dev_net(hard_iface->soft_iface);
 	real_net = batadv_getlink_net(netdev, net);
+
+	/* iflink to itself, most likely physical device */
+	if (net == real_net && netdev->ifindex == iflink) {
+		real_netdev = netdev;
+		dev_hold(real_netdev);
+		goto out;
+	}
+
 	real_netdev = dev_get_by_index(real_net, iflink);
 
 out: