Messages in this thread | | | Date | Tue, 6 Jun 2023 16:28:02 +0200 | Subject | Re: POSSIBLE BUG: selftests/net/fcnal-test.sh: [FAIL] in vrf "bind - ns-B IPv6 LLA" test | From | Mirsad Todorovac <> |
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On 6/6/23 16:11, Guillaume Nault wrote: > On Tue, Jun 06, 2023 at 03:57:35PM +0200, Mirsad Todorovac wrote: >> diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c >> index c4835dbdfcff..c1d81c49b775 100644 >> --- a/net/ipv6/ping.c >> +++ b/net/ipv6/ping.c >> @@ -73,6 +73,10 @@ static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) >> struct rt6_info *rt; >> struct pingfakehdr pfh; >> struct ipcm6_cookie ipc6; >> + struct net *net = sock_net(sk); >> + struct net_device *dev = NULL; >> + struct net_device *mdev = NULL; >> + struct net_device *bdev = NULL; >> >> err = ping_common_sendmsg(AF_INET6, msg, len, &user_icmph, >> sizeof(user_icmph)); >> @@ -111,10 +115,26 @@ static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) >> else if (!oif) >> oif = np->ucast_oif; >> >> + if (oif) { >> + rcu_read_lock(); >> + dev = dev_get_by_index_rcu(net, oif); >> + rcu_read_unlock(); > > You can't assume '*dev' is still valid after rcu_read_unlock() unless > you hold a reference on it. > >> + rtnl_lock(); >> + mdev = netdev_master_upper_dev_get(dev); >> + rtnl_unlock(); > > Because of that, 'dev' might have already disappeared at the time > netdev_master_upper_dev_get() is called. So it may dereference an > invalid pointer here.
Good point, thanks. I didn't expect those to change.
This can be fixed, provided that RCU and RTNL locks can be nested:
rcu_read_lock(); if (oif) { dev = dev_get_by_index_rcu(net, oif); rtnl_lock(); mdev = netdev_master_upper_dev_get(dev); rtnl_unlock(); }
if (sk->sk_bound_dev_if) { bdev = dev_get_by_index_rcu(net, sk->sk_bound_dev_if); }
addr_type = ipv6_addr_type(daddr); if ((__ipv6_addr_needs_scope_id(addr_type) && !oif) || (addr_type & IPV6_ADDR_MAPPED) || (oif && sk->sk_bound_dev_if && oif != sk->sk_bound_dev_if && !(mdev && sk->sk_bound_dev_if && bdev && mdev == bdev))) { rcu_read_unlock(); return -EINVAL; } rcu_read_unlock();
But again this is still probably not race-free (bdev might also disappear before the mdev == bdev test), even if it passed fcnal-test.sh, there is much duplication of code, so your one-line solution is obviously by far better. :-)
Much obliged.
Best regards, Mirsad
>> + } >> + >> + if (sk->sk_bound_dev_if) { >> + rcu_read_lock(); >> + bdev = dev_get_by_index_rcu(net, sk->sk_bound_dev_if); >> + rcu_read_unlock(); >> + } >> + >> addr_type = ipv6_addr_type(daddr); >> if ((__ipv6_addr_needs_scope_id(addr_type) && !oif) || >> (addr_type & IPV6_ADDR_MAPPED) || >> - (oif && sk->sk_bound_dev_if && oif != sk->sk_bound_dev_if)) >> + (oif && sk->sk_bound_dev_if && oif != sk->sk_bound_dev_if && >> + !(mdev && sk->sk_bound_dev_if && bdev && mdev == bdev))) >> return -EINVAL; >> >> ipcm6_init_sk(&ipc6, np); >> >> However, this works by the test (888 passed) but your two liner is obviously >> better :-) > > :)
-- Mirsad Goran Todorovac Sistem inženjer Grafički fakultet | Akademija likovnih umjetnosti Sveučilište u Zagrebu
System engineer Faculty of Graphic Arts | Academy of Fine Arts University of Zagreb, Republic of Croatia
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