On 1/9/19 2:57 AM, Ido Schimmel wrote:
> IPv4 routing tables are flushed in two cases:
>
> 1. In response to events in the netdev and inetaddr notification chains
> 2. When a network namespace is being dismantled
>
> In both cases only routes associated with a dead nexthop group are
> flushed. However, a nexthop group will only be marked as dead in case it
> is populated with actual nexthops using a nexthop device. This is not
> the case when the route in question is an error route (e.g.,
> 'blackhole', 'unreachable').
>
> Therefore, when a network namespace is being dismantled such routes are
> not flushed and leaked [1].
>
> To reproduce:
> # ip netns add blue
> # ip -n blue route add unreachable 192.0.2.0/24
> # ip netns del blue
>
> Fix this by not skipping error routes that are not marked with
> RTNH_F_DEAD when flushing the routing tables.
>
> To prevent the flushing of such routes in case #1, add a parameter to
> fib_table_flush() that indicates if the table is flushed as part of
> namespace dismantle or not.
>
> Note that this problem does not exist in IPv6 since error routes are
> associated with the loopback device.
>
> [1]
> unreferenced object 0xffff888066650338 (size 56):
> comm "ip", pid 1206, jiffies 4294786063 (age 26.235s)
> hex dump (first 32 bytes):
> 00 00 00 00 00 00 00 00 b0 1c 62 61 80 88 ff ff ..........ba....
> e8 8b a1 64 80 88 ff ff 00 07 00 08 fe 00 00 00 ...d............
> backtrace:
> [<00000000856ed27d>] inet_rtm_newroute+0x129/0x220
> [<00000000fcdfc00a>] rtnetlink_rcv_msg+0x397/0xa20
> [<00000000cb85801a>] netlink_rcv_skb+0x132/0x380
> [<00000000ebc991d2>] netlink_unicast+0x4c0/0x690
> [<0000000014f62875>] netlink_sendmsg+0x929/0xe10
> [<00000000bac9d967>] sock_sendmsg+0xc8/0x110
> [<00000000223e6485>] ___sys_sendmsg+0x77a/0x8f0
> [<000000002e94f880>] __sys_sendmsg+0xf7/0x250
> [<00000000ccb1fa72>] do_syscall_64+0x14d/0x610
> [<00000000ffbe3dae>] entry_SYSCALL_64_after_hwframe+0x49/0xbe
> [<000000003a8b605b>] 0xffffffffffffffff
> unreferenced object 0xffff888061621c88 (size 48):
> comm "ip", pid 1206, jiffies 4294786063 (age 26.235s)
> hex dump (first 32 bytes):
> 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
> 6b 6b 6b 6b 6b 6b 6b 6b d8 8e 26 5f 80 88 ff ff kkkkkkkk..&_....
> backtrace:
> [<00000000733609e3>] fib_table_insert+0x978/0x1500
> [<00000000856ed27d>] inet_rtm_newroute+0x129/0x220
> [<00000000fcdfc00a>] rtnetlink_rcv_msg+0x397/0xa20
> [<00000000cb85801a>] netlink_rcv_skb+0x132/0x380
> [<00000000ebc991d2>] netlink_unicast+0x4c0/0x690
> [<0000000014f62875>] netlink_sendmsg+0x929/0xe10
> [<00000000bac9d967>] sock_sendmsg+0xc8/0x110
> [<00000000223e6485>] ___sys_sendmsg+0x77a/0x8f0
> [<000000002e94f880>] __sys_sendmsg+0xf7/0x250
> [<00000000ccb1fa72>] do_syscall_64+0x14d/0x610
> [<00000000ffbe3dae>] entry_SYSCALL_64_after_hwframe+0x49/0xbe
> [<000000003a8b605b>] 0xffffffffffffffff
>
> Fixes: 8cced9eff1d4 ("[NETNS]: Enable routing configuration in non-initial
> namespace.")
> Signed-off-by: Ido Schimmel <ido...@mellanox.com>
> ---
> include/net/ip_fib.h | 2 +-
> net/ipv4/fib_frontend.c | 4 ++--
> net/ipv4/fib_trie.c | 15 ++++++++++++---
> 3 files changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
> index c5969762a8f4..9c8214d2116d 100644
> --- a/include/net/ip_fib.h
> +++ b/include/net/ip_fib.h
> @@ -241,7 +241,7 @@ int fib_table_delete(struct net *, struct fib_table *,
> struct fib_config *,
> struct netlink_ext_ack *extack);
> int fib_table_dump(struct fib_table *table, struct sk_buff *skb,
> struct netlink_callback *cb, struct fib_dump_filter *filter);
> -int fib_table_flush(struct net *net, struct fib_table *table);
> +int fib_table_flush(struct net *net, struct fib_table *table, bool
> flush_all);
> struct fib_table *fib_trie_unmerge(struct fib_table *main_tb);
> void fib_table_flush_external(struct fib_table *table);
> void fib_free_table(struct fib_table *tb);
> diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
> index 6df95be96311..fe4f6a624238 100644
> --- a/net/ipv4/fib_frontend.c
> +++ b/net/ipv4/fib_frontend.c
> @@ -203,7 +203,7 @@ static void fib_flush(struct net *net)
> struct fib_table *tb;
>
> hlist_for_each_entry_safe(tb, tmp, head, tb_hlist)
> - flushed += fib_table_flush(net, tb);
> + flushed += fib_table_flush(net, tb, false);
> }
>
> if (flushed)
> @@ -1463,7 +1463,7 @@ static void ip_fib_net_exit(struct net *net)
>
> hlist_for_each_entry_safe(tb, tmp, head, tb_hlist) {
> hlist_del(&tb->tb_hlist);
> - fib_table_flush(net, tb);
> + fib_table_flush(net, tb, true);
> fib_free_table(tb);
> }
> }
> diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
> index 237c9f72b265..a573e37e0615 100644
> --- a/net/ipv4/fib_trie.c
> +++ b/net/ipv4/fib_trie.c
> @@ -1856,7 +1856,7 @@ void fib_table_flush_external(struct fib_table *tb)
> }
>
> /* Caller must hold RTNL. */
> -int fib_table_flush(struct net *net, struct fib_table *tb)
> +int fib_table_flush(struct net *net, struct fib_table *tb, bool flush_all)
> {
> struct trie *t = (struct trie *)tb->tb_data;
> struct key_vector *pn = t->kv;
> @@ -1904,8 +1904,17 @@ int fib_table_flush(struct net *net, struct fib_table
> *tb)
> hlist_for_each_entry_safe(fa, tmp, &n->leaf, fa_list) {
> struct fib_info *fi = fa->fa_info;
>
> - if (!fi || !(fi->fib_flags & RTNH_F_DEAD) ||
> - tb->tb_id != fa->tb_id) {
> + if (!fi || tb->tb_id != fa->tb_id ||
> + (!(fi->fib_flags & RTNH_F_DEAD) &&
> + !fib_props[fa->fa_type].error)) {
> + slen = fa->fa_slen;
> + continue;
> + }
> +
> + /* Do not flush error routes if network namespace is
> + * not being dismantled
> + */
The double negative makes that comment more difficult than necessary,
but the logic looks good.
Reviewed-by: David Ahern <dsah...@gmail.com>
> + if (!flush_all && fib_props[fa->fa_type].error) {
> slen = fa->fa_slen;
> continue;
> }
>
