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Date: Sun, 6 Feb 2022 07:56:00 -0800
From: Eric Dumazet <eric.dumazet@...il.com>
To: "David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>
Cc: netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>,
syzbot <syzkaller@...glegroups.com>
Subject: [PATCH net-next] ip6mr: fix use-after-free in ip6mr_sk_done()
From: Eric Dumazet <edumazet@...gle.com>
Apparently addrconf_exit_net() is called before igmp6_net_exit()
and ndisc_net_exit() at netns dismantle time:
net_namespace: call ip6table_mangle_net_exit()
net_namespace: call ip6_tables_net_exit()
net_namespace: call ipv6_sysctl_net_exit()
net_namespace: call ioam6_net_exit()
net_namespace: call seg6_net_exit()
net_namespace: call ping_v6_proc_exit_net()
net_namespace: call tcpv6_net_exit()
ip6mr_sk_done sk=ffffa354c78a74c0
net_namespace: call ipv6_frags_exit_net()
net_namespace: call addrconf_exit_net()
net_namespace: call ip6addrlbl_net_exit()
net_namespace: call ip6_flowlabel_net_exit()
net_namespace: call ip6_route_net_exit_late()
net_namespace: call fib6_rules_net_exit()
net_namespace: call xfrm6_net_exit()
net_namespace: call fib6_net_exit()
net_namespace: call ip6_route_net_exit()
net_namespace: call ipv6_inetpeer_exit()
net_namespace: call if6_proc_net_exit()
net_namespace: call ipv6_proc_exit_net()
net_namespace: call udplite6_proc_exit_net()
net_namespace: call raw6_exit_net()
net_namespace: call igmp6_net_exit()
ip6mr_sk_done sk=ffffa35472b2a180
ip6mr_sk_done sk=ffffa354c78a7980
net_namespace: call ndisc_net_exit()
ip6mr_sk_done sk=ffffa35472b2ab00
net_namespace: call ip6mr_net_exit()
net_namespace: call inet6_net_exit()
This was fine because ip6mr_sk_done() would not reach the point decreasing
net->ipv6.devconf_all->mc_forwarding until my patch in ip6mr_sk_done().
To fix this without changing struct pernet_operations ordering,
we can clear net->ipv6.devconf_dflt and net->ipv6.devconf_all
when they are freed from addrconf_exit_net()
BUG: KASAN: use-after-free in instrument_atomic_read include/linux/instrumented.h:71 [inline]
BUG: KASAN: use-after-free in atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
BUG: KASAN: use-after-free in ip6mr_sk_done+0x11b/0x410 net/ipv6/ip6mr.c:1578
Read of size 4 at addr ffff88801ff08688 by task kworker/u4:4/963
CPU: 0 PID: 963 Comm: kworker/u4:4 Not tainted 5.17.0-rc2-syzkaller-00650-g5a8fb33e5305 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_address_description.constprop.0.cold+0x8d/0x336 mm/kasan/report.c:255
__kasan_report mm/kasan/report.c:442 [inline]
kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
instrument_atomic_read include/linux/instrumented.h:71 [inline]
atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
ip6mr_sk_done+0x11b/0x410 net/ipv6/ip6mr.c:1578
rawv6_close+0x58/0x80 net/ipv6/raw.c:1201
inet_release+0x12e/0x280 net/ipv4/af_inet.c:428
inet6_release+0x4c/0x70 net/ipv6/af_inet6.c:478
__sock_release net/socket.c:650 [inline]
sock_release+0x87/0x1b0 net/socket.c:678
inet_ctl_sock_destroy include/net/inet_common.h:65 [inline]
igmp6_net_exit+0x6b/0x170 net/ipv6/mcast.c:3173
ops_exit_list+0xb0/0x170 net/core/net_namespace.c:168
cleanup_net+0x4ea/0xb00 net/core/net_namespace.c:600
process_one_work+0x9ac/0x1650 kernel/workqueue.c:2307
worker_thread+0x657/0x1110 kernel/workqueue.c:2454
kthread+0x2e9/0x3a0 kernel/kthread.c:377
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
Fixes: f2f2325ec799 ("ip6mr: ip6mr_sk_done() can exit early in common cases")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: syzbot <syzkaller@...glegroups.com>
---
net/ipv6/addrconf.c | 2 ++
net/ipv6/ip6mr.c | 10 ++++++----
2 files changed, 8 insertions(+), 4 deletions(-)
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index ff1b2484b8ed8638e4d37eb21c67de4e5ac43dae..ef23e7dc538ad983a28853865dd4281f7f0ea8de 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -7184,7 +7184,9 @@ static void __net_exit addrconf_exit_net(struct net *net)
NETCONFA_IFINDEX_ALL);
#endif
kfree(net->ipv6.devconf_dflt);
+ net->ipv6.devconf_dflt = NULL;
kfree(net->ipv6.devconf_all);
+ net->ipv6.devconf_all = NULL;
}
static struct pernet_operations addrconf_ops = {
diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index 8e483e14b5709b1b8a6e9dfd6616a5bde5c273ee..fd660414d482a30c6d339bb7360bd91d8f3c6f05 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -1567,15 +1567,17 @@ static int ip6mr_sk_init(struct mr_table *mrt, struct sock *sk)
int ip6mr_sk_done(struct sock *sk)
{
+ struct net *net = sock_net(sk);
+ struct ipv6_devconf *devconf;
+ struct mr_table *mrt;
int err = -EACCES;
- struct net *net = sock_net(sk);
- struct mr_table *mrt;
if (sk->sk_type != SOCK_RAW ||
inet_sk(sk)->inet_num != IPPROTO_ICMPV6)
return err;
- if (!atomic_read(&net->ipv6.devconf_all->mc_forwarding))
+ devconf = net->ipv6.devconf_all;
+ if (!devconf || !atomic_read(&devconf->mc_forwarding))
return err;
rtnl_lock();
@@ -1587,7 +1589,7 @@ int ip6mr_sk_done(struct sock *sk)
* so the RCU grace period before sk freeing
* is guaranteed by sk_destruct()
*/
- atomic_dec(&net->ipv6.devconf_all->mc_forwarding);
+ atomic_dec(&devconf->mc_forwarding);
write_unlock_bh(&mrt_lock);
inet6_netconf_notify_devconf(net, RTM_NEWNETCONF,
NETCONFA_MC_FORWARDING,
--
2.35.0.263.gb82422642f-goog
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