diff options
author | Eric Dumazet <edumazet@google.com> | 2019-11-07 09:26:19 -0800 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2019-11-07 16:13:13 -0800 |
commit | 1bef4c223b8588cf50433bdc2c6953d82949b3b3 (patch) | |
tree | fe890d18db1b61394fa70f01d0547649cd0269df /net/ipv6 | |
parent | bf5a6b4c474c589244dc25ee1af2c3c829228ef8 (diff) |
ipv6: fixes rt6_probe() and fib6_nh->last_probe init
While looking at a syzbot KCSAN report [1], I found multiple
issues in this code :
1) fib6_nh->last_probe has an initial value of 0.
While probably okay on 64bit kernels, this causes an issue
on 32bit kernels since the time_after(jiffies, 0 + interval)
might be false ~24 days after boot (for HZ=1000)
2) The data-race found by KCSAN
I could use READ_ONCE() and WRITE_ONCE(), but we also can
take the opportunity of not piling-up too many rt6_probe_deferred()
works by using instead cmpxchg() so that only one cpu wins the race.
[1]
BUG: KCSAN: data-race in find_match / find_match
write to 0xffff8880bb7aabe8 of 8 bytes by interrupt on cpu 1:
rt6_probe net/ipv6/route.c:663 [inline]
find_match net/ipv6/route.c:757 [inline]
find_match+0x5bd/0x790 net/ipv6/route.c:733
__find_rr_leaf+0xe3/0x780 net/ipv6/route.c:831
find_rr_leaf net/ipv6/route.c:852 [inline]
rt6_select net/ipv6/route.c:896 [inline]
fib6_table_lookup+0x383/0x650 net/ipv6/route.c:2164
ip6_pol_route+0xee/0x5c0 net/ipv6/route.c:2200
ip6_pol_route_output+0x48/0x60 net/ipv6/route.c:2452
fib6_rule_lookup+0x3d6/0x470 net/ipv6/fib6_rules.c:117
ip6_route_output_flags_noref+0x16b/0x230 net/ipv6/route.c:2484
ip6_route_output_flags+0x50/0x1a0 net/ipv6/route.c:2497
ip6_dst_lookup_tail+0x25d/0xc30 net/ipv6/ip6_output.c:1049
ip6_dst_lookup_flow+0x68/0x120 net/ipv6/ip6_output.c:1150
inet6_csk_route_socket+0x2f7/0x420 net/ipv6/inet6_connection_sock.c:106
inet6_csk_xmit+0x91/0x1f0 net/ipv6/inet6_connection_sock.c:121
__tcp_transmit_skb+0xe81/0x1d60 net/ipv4/tcp_output.c:1169
tcp_transmit_skb net/ipv4/tcp_output.c:1185 [inline]
tcp_xmit_probe_skb+0x19b/0x1d0 net/ipv4/tcp_output.c:3735
read to 0xffff8880bb7aabe8 of 8 bytes by interrupt on cpu 0:
rt6_probe net/ipv6/route.c:657 [inline]
find_match net/ipv6/route.c:757 [inline]
find_match+0x521/0x790 net/ipv6/route.c:733
__find_rr_leaf+0xe3/0x780 net/ipv6/route.c:831
find_rr_leaf net/ipv6/route.c:852 [inline]
rt6_select net/ipv6/route.c:896 [inline]
fib6_table_lookup+0x383/0x650 net/ipv6/route.c:2164
ip6_pol_route+0xee/0x5c0 net/ipv6/route.c:2200
ip6_pol_route_output+0x48/0x60 net/ipv6/route.c:2452
fib6_rule_lookup+0x3d6/0x470 net/ipv6/fib6_rules.c:117
ip6_route_output_flags_noref+0x16b/0x230 net/ipv6/route.c:2484
ip6_route_output_flags+0x50/0x1a0 net/ipv6/route.c:2497
ip6_dst_lookup_tail+0x25d/0xc30 net/ipv6/ip6_output.c:1049
ip6_dst_lookup_flow+0x68/0x120 net/ipv6/ip6_output.c:1150
inet6_csk_route_socket+0x2f7/0x420 net/ipv6/inet6_connection_sock.c:106
inet6_csk_xmit+0x91/0x1f0 net/ipv6/inet6_connection_sock.c:121
__tcp_transmit_skb+0xe81/0x1d60 net/ipv4/tcp_output.c:1169
Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 18894 Comm: udevd Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Fixes: cc3a86c802f0 ("ipv6: Change rt6_probe to take a fib6_nh")
Fixes: f547fac624be ("ipv6: rate-limit probes for neighbourless routes")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6')
-rw-r--r-- | net/ipv6/route.c | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/net/ipv6/route.c b/net/ipv6/route.c index a63ff85fe141..e60bf8e7dd1a 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -621,6 +621,7 @@ static void rt6_probe(struct fib6_nh *fib6_nh) { struct __rt6_probe_work *work = NULL; const struct in6_addr *nh_gw; + unsigned long last_probe; struct neighbour *neigh; struct net_device *dev; struct inet6_dev *idev; @@ -639,6 +640,7 @@ static void rt6_probe(struct fib6_nh *fib6_nh) nh_gw = &fib6_nh->fib_nh_gw6; dev = fib6_nh->fib_nh_dev; rcu_read_lock_bh(); + last_probe = READ_ONCE(fib6_nh->last_probe); idev = __in6_dev_get(dev); neigh = __ipv6_neigh_lookup_noref(dev, nh_gw); if (neigh) { @@ -654,13 +656,15 @@ static void rt6_probe(struct fib6_nh *fib6_nh) __neigh_set_probe_once(neigh); } write_unlock(&neigh->lock); - } else if (time_after(jiffies, fib6_nh->last_probe + + } else if (time_after(jiffies, last_probe + idev->cnf.rtr_probe_interval)) { work = kmalloc(sizeof(*work), GFP_ATOMIC); } - if (work) { - fib6_nh->last_probe = jiffies; + if (!work || cmpxchg(&fib6_nh->last_probe, + last_probe, jiffies) != last_probe) { + kfree(work); + } else { INIT_WORK(&work->work, rt6_probe_deferred); work->target = *nh_gw; dev_hold(dev); @@ -3383,6 +3387,9 @@ int fib6_nh_init(struct net *net, struct fib6_nh *fib6_nh, int err; fib6_nh->fib_nh_family = AF_INET6; +#ifdef CONFIG_IPV6_ROUTER_PREF + fib6_nh->last_probe = jiffies; +#endif err = -ENODEV; if (cfg->fc_ifindex) { |