Re: [PATCH] net: check for NULL net_device in FIB tables
From: Julian Anastasov <ja@ssi.bg>
Date: 2016-07-04 19:46:01
Hello, On Mon, 4 Jul 2016, Vegard Nossum wrote:
struct fib_nh->nh_dev can be NULL, so we should check it before calling __in_dev_get_rcu on it. Multiple places seem to want this (and check the return value), so we can add a convenience wrapper for this. This fixes a crash in AF_NETLINK sendmsg(). Please double check that I caught all the callers that need the NULL guard.
What kind of configuration causes such crash?
quoted hunk ↗ jump to hunk
Fixes: 0eeb075fad73 ("net: ipv4 sysctl option to ignore routes when nexthop link is down") Cc: Andy Gospodarek <redacted> Cc: Dinesh Dutt <redacted> Cc: Scott Feldman <redacted> Cc: David S. Miller <davem@davemloft.net> Signed-off-by: Vegard Nossum <redacted> --- include/linux/inetdevice.h | 7 +++++++ net/ipv4/fib_semantics.c | 8 ++++---- 2 files changed, 11 insertions(+), 4 deletions(-)diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h index ee971f3..2d8bea1 100644 --- a/include/linux/inetdevice.h +++ b/include/linux/inetdevice.h@@ -222,6 +222,13 @@ static inline struct in_device *__in_dev_get_rtnl(const struct net_device *dev) return rtnl_dereference(dev->ip_ptr); } +static inline struct in_device *in_dev_get_rtnl(const struct net_device *dev) +{ + if (!dev) + return NULL; + return __in_dev_get_rtnl(dev); +} + static inline struct neigh_parms *__in_dev_arp_parms_get_rcu(const struct net_device *dev) { struct in_device *in_dev = __in_dev_get_rcu(dev);diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c index d09173b..8289799 100644 --- a/net/ipv4/fib_semantics.c +++ b/net/ipv4/fib_semantics.c@@ -545,7 +545,7 @@ static void fib_rebalance(struct fib_info *fi) if (nh->nh_flags & RTNH_F_DEAD) continue; - in_dev = __in_dev_get_rtnl(nh->nh_dev); + in_dev = in_dev_get_rtnl(nh->nh_dev);
fib_rebalance can not crash because for multipath routes (fib_nhs > 1) all nexthops should have valid nh_dev.
quoted hunk ↗ jump to hunk
if (in_dev && IN_DEV_IGNORE_ROUTES_WITH_LINKDOWN(in_dev) &&@@ -559,7 +559,7 @@ static void fib_rebalance(struct fib_info *fi) change_nexthops(fi) { int upper_bound; - in_dev = __in_dev_get_rtnl(nexthop_nh->nh_dev); + in_dev = in_dev_get_rtnl(nexthop_nh->nh_dev); if (nexthop_nh->nh_flags & RTNH_F_DEAD) { upper_bound = -1;@@ -1261,7 +1261,7 @@ int fib_dump_info(struct sk_buff *skb, u32 portid, u32 seq, int event, nla_put_u32(skb, RTA_OIF, fi->fib_nh->nh_oif)) goto nla_put_failure; if (fi->fib_nh->nh_flags & RTNH_F_LINKDOWN) { - in_dev = __in_dev_get_rtnl(fi->fib_nh->nh_dev); + in_dev = in_dev_get_rtnl(fi->fib_nh->nh_dev);
Looks like this is the only place that can crash, adding extra cycles to the other places is not good. And this can happen only because fib_create_info() allows RTNH_F_LINKDOWN to come for routes with error. May be fc_flags should be masked there? Or there is another place that sets the flag when nh_dev is NULL?
quoted hunk ↗ jump to hunk
if (in_dev && IN_DEV_IGNORE_ROUTES_WITH_LINKDOWN(in_dev)) rtm->rtm_flags |= RTNH_F_DEAD;@@ -1292,7 +1292,7 @@ int fib_dump_info(struct sk_buff *skb, u32 portid, u32 seq, int event, rtnh->rtnh_flags = nh->nh_flags & 0xFF; if (nh->nh_flags & RTNH_F_LINKDOWN) { - in_dev = __in_dev_get_rtnl(nh->nh_dev); + in_dev = in_dev_get_rtnl(nh->nh_dev);
Not needed because fib_nhs > 1
if (in_dev && IN_DEV_IGNORE_ROUTES_WITH_LINKDOWN(in_dev)) rtnh->rtnh_flags |= RTNH_F_DEAD; --
Regards