Re: Division by zero on UP (was: Re: netfilter: nat: use keyed locks)

From: Florian Westphal
Date: Sun Sep 10 2017 - 07:24:38 EST


Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
> > srchash = hash_by_src(net,
> > &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
> > - spin_lock_bh(&nf_nat_lock);
> > + lock = &nf_nat_locks[srchash % ARRAY_SIZE(nf_nat_locks)];
> > + spin_lock_bh(lock);
>
> If no spinlock debugging options (CONFIG_GENERIC_LOCKBREAK,
> CONFIG_DEBUG_SPINLOCK, CONFIG_DEBUG_LOCK_ALLOC) are enabled on a UP platform
> (e.g. m68k defconfig), arch_spinlock_t is an empty struct, and thus
> ARRAY_SIZE(nf_nat_locks)] is zero, leading to:
>
> net/netfilter/nf_nat_core.c: In function ânf_nat_setup_infoâ:
> net/netfilter/nf_nat_core.c:432: warning: division by zero

Gah. Sorry. This is the 2nd time I add such a bug :(

Can you send a patch? It should be enough to use CONNTRACK_LOCKS
instead of ARRAY_SIZE(nf_nat_locks) to avoid this problem.

Otherwise I will take care of this next thing monday morning.