From: Ido Schimmel Date: Fri, 28 Jul 2017 20:27:44 +0000 (+0300) Subject: ipv4: fib: Fix NULL pointer deref during fib_sync_down_dev() X-Git-Tag: v4.12.6~7 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a0ed1f0346decfecb33afc77f333c3f38f1660dd;p=thirdparty%2Fkernel%2Fstable.git ipv4: fib: Fix NULL pointer deref during fib_sync_down_dev() [ Upstream commit 71ed7ee35ad2c5300f4b51634185a0193b4fb0fa ] Michał reported a NULL pointer deref during fib_sync_down_dev() when unregistering a netdevice. The problem is that we don't check for 'in_dev' being NULL, which can happen in very specific cases. Usually routes are flushed upon NETDEV_DOWN sent in either the netdev or the inetaddr notification chains. However, if an interface isn't configured with any IP address, then it's possible for host routes to be flushed following NETDEV_UNREGISTER, after NULLing dev->ip_ptr in inetdev_destroy(). To reproduce: $ ip link add type dummy $ ip route add local 1.1.1.0/24 dev dummy0 $ ip link del dev dummy0 Fix this by checking for the presence of 'in_dev' before referencing it. Fixes: 982acb97560c ("ipv4: fib: Notify about nexthop status changes") Signed-off-by: Ido Schimmel Reported-by: Michał Mirosław Tested-by: Michał Mirosław Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c index ad9ad4aab5da7..ce7bc2e5175af 100644 --- a/net/ipv4/fib_semantics.c +++ b/net/ipv4/fib_semantics.c @@ -1372,7 +1372,7 @@ static int call_fib_nh_notifiers(struct fib_nh *fib_nh, return call_fib_notifiers(dev_net(fib_nh->nh_dev), event_type, &info.info); case FIB_EVENT_NH_DEL: - if ((IN_DEV_IGNORE_ROUTES_WITH_LINKDOWN(in_dev) && + if ((in_dev && IN_DEV_IGNORE_ROUTES_WITH_LINKDOWN(in_dev) && fib_nh->nh_flags & RTNH_F_LINKDOWN) || (fib_nh->nh_flags & RTNH_F_DEAD)) return call_fib_notifiers(dev_net(fib_nh->nh_dev),