Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote:
> On Thu, Oct 25, 2018 at 11:56:12PM +0900, Taehee Yoo wrote:
> > conn_free() holds lock with spin_lock(). and it is called by both
> > nf_conncount_lookup() and nf_conncount_gc_list().
> > nf_conncount_lookup() is bottom-half context and nf_conncount_gc_list()
> > is process context. so that spin_lock() is not safe.
> > Hence conn_free() should use spin_lock_bh() instead of spin_lock().
> >
> > test commands:
> > %nft add table ip filter
> > %nft add chain ip filter input { type filter hook input priority 0\; }
> > %nft add rule filter input meter test { ip saddr ct count over 2 } \
> > counter
> >
> > splat looks like:
> > [ 461.996507] ================================
> > [ 461.998999] WARNING: inconsistent lock state
> > [ 461.998999] 4.19.0-rc6+ #22 Not tainted
> > [ 461.998999] --------------------------------
> > [ 461.998999] inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
> > [ 461.998999] kworker/0:2/134 [HC0[0]:SC0[0]:HE1:SE1] takes:
> > [ 461.998999] 00000000a71a559a (&(&list->list_lock)->rlock){+.?.}, at: conn_free+0x69/0x2b0 [nf_conncount]
> > [ 461.998999] {IN-SOFTIRQ-W} state was registered at:
> > [ 461.998999] _raw_spin_lock+0x30/0x70
> > [ 461.998999] nf_conncount_add+0x28a/0x520 [nf_conncount]
> > [ 461.998999] nft_connlimit_eval+0x401/0x580 [nft_connlimit]
> > [ 461.998999] nft_dynset_eval+0x32b/0x590 [nf_tables]
> > [ 461.998999] nft_do_chain+0x497/0x1430 [nf_tables]
> > [ 461.998999] nft_do_chain_ipv4+0x255/0x330 [nf_tables]
> > [ 461.998999] nf_hook_slow+0xb1/0x160
> > [ ... ]
> > [ 461.998999] other info that might help us debug this:
> > [ 461.998999] Possible unsafe locking scenario:
> > [ 461.998999]
> > [ 461.998999] CPU0
> > [ 461.998999] ----
> > [ 461.998999] lock(&(&list->list_lock)->rlock);
> > [ 461.998999] <Interrupt>
> > [ 461.998999] lock(&(&list->list_lock)->rlock);
> > [ 461.998999]
> > [ 461.998999] *** DEADLOCK ***
> > [ 461.998999]
> > [ ... ]
>
> nf_conncount_add() also holds spin_lock while allocate from there is
> GFP_ATOMIC given this is called from packet path.
Good catch, yes, this needs spin_lock_bh variant too.
> tree_nodes_free() is also called from user context without _bh
> disabled.
This one is fine, both call sites hold spin_lock_bh(&nf_conncount_locks[x]).
