On 10/30/17 9:53 PM, Eric Dumazet wrote:
> David, I was looking at addrconf_permanent_addr() and wondered
> if there is not some problem with it.
>
> It seems we need to increment ifp refcount before calling
> ipv6_del_addr()
>
> Could you double check if this patch is needed, I am guessing you have a
> test suite exercising this code path ?
A lot has changed in 20 months since the patch that added the code. For
instance, taking down the 'lo' device no longer affects host routes on
other interfaces. Also, fixup_permanent_addr only fails on memory
allocation. Did you hit this with a test case because I do not have a
general one that causes the memory failure (hard coding a failure for an
address is the only way).
>
> Thanks.
>
> PS : Presumably CONFIG_REFCOUNT_FULL=y should have warned you of the
> problem.
I have not run a debug kernel in a while -- and did not have this option
set. Added it to my debug config.
>
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index
> 4a96ebbf8eda5f59a6ff88e836d666a404d2bf0d..8a1c846d3df949a4638589f187120db22a3525ba
> 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -3335,6 +3335,7 @@ static void addrconf_permanent_addr(struct net_device
> *dev)
> if ((ifp->flags & IFA_F_PERMANENT) &&
> fixup_permanent_addr(idev, ifp) < 0) {
> write_unlock_bh(&idev->lock);
> + in6_ifa_hold(ifp);
> ipv6_del_addr(ifp);
> write_lock_bh(&idev->lock);
>
Yes, forcing a failure here does trigger refcnt warning, but then you
knew that. ;-)
PS. is the following a known failure? I triggered it looking into your
report
[ 170.385741] ======================================================
[ 170.387490] WARNING: possible circular locking dependency detected
[ 170.389214] 4.14.0-rc5+ #338 Not tainted
[ 170.390323] ------------------------------------------------------
[ 170.392017] swapper/0/0 is trying to acquire lock:
[ 170.393408] (slock-AF_INET){+.-.}, at: [<ffffffff8172848b>]
tcp_delack_timer+0x29/0xb1
[ 170.395622]
but task is already holding lock:
[ 170.396943] ((timer)){+.-.}, at: [<ffffffff810f3c53>]
call_timer_fn+0x5/0x36b
[ 170.397912]
which lock already depends on the new lock.
[ 170.398986]
the existing dependency chain (in reverse order) is:
[ 170.399965]
-> #1 ((timer)){+.-.}:
[ 170.400629] lock_acquire+0x154/0x220
[ 170.401198] del_timer_sync+0x47/0xbd
[ 170.401760] inet_csk_reqsk_queue_drop+0x109/0x141
[ 170.402464] inet_csk_complete_hashdance+0x3b/0x68
[ 170.403173] tcp_check_req+0x517/0x5f1
[ 170.403746] tcp_v4_rcv+0x6ad/0xce7
[ 170.404287] ip_local_deliver_finish+0x1d4/0x281
[ 170.404985] ip_local_deliver+0xaf/0xcf
[ 170.405571] ip_rcv_finish+0x632/0x6ff
[ 170.406140] ip_rcv+0x45d/0x4a6
...
