From 88fd8709858b9cd94e2d28b4b3cac4b752f0683a Mon Sep 17 00:00:00 2001 From: bill bonaparte Date: Thu, 6 Nov 2014 14:36:48 +0100 Subject: netfilter: conntrack: fix race in __nf_conntrack_confirm against get_next_corpse commit 5195c14c8b27cc0b18220ddbf0e5ad3328a04187 upstream. After removal of the central spinlock nf_conntrack_lock, in commit 93bb0ceb75be2 ("netfilter: conntrack: remove central spinlock nf_conntrack_lock"), it is possible to race against get_next_corpse(). The race is against the get_next_corpse() cleanup on the "unconfirmed" list (a per-cpu list with seperate locking), which set the DYING bit. Fix this race, in __nf_conntrack_confirm(), by removing the CT from unconfirmed list before checking the DYING bit. In case race occured, re-add the CT to the dying list. While at this, fix coding style of the comment that has been updated. Fixes: 93bb0ceb75be2 ("netfilter: conntrack: remove central spinlock nf_conntrack_lock") Reported-by: bill bonaparte Signed-off-by: bill bonaparte Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Pablo Neira Ayuso Signed-off-by: Greg Kroah-Hartman --- net/netfilter/nf_conntrack_core.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c index de88c4ab5146..ec94ba94079f 100644 --- a/net/netfilter/nf_conntrack_core.c +++ b/net/netfilter/nf_conntrack_core.c @@ -611,12 +611,16 @@ __nf_conntrack_confirm(struct sk_buff *skb) */ NF_CT_ASSERT(!nf_ct_is_confirmed(ct)); pr_debug("Confirming conntrack %p\n", ct); - /* We have to check the DYING flag inside the lock to prevent - a race against nf_ct_get_next_corpse() possibly called from - user context, else we insert an already 'dead' hash, blocking - further use of that particular connection -JM */ + + /* We have to check the DYING flag after unlink to prevent + * a race against nf_ct_get_next_corpse() possibly called from + * user context, else we insert an already 'dead' hash, blocking + * further use of that particular connection -JM. + */ + nf_ct_del_from_dying_or_unconfirmed_list(ct); if (unlikely(nf_ct_is_dying(ct))) { + nf_ct_add_to_dying_list(ct); nf_conntrack_double_unlock(hash, reply_hash); local_bh_enable(); return NF_ACCEPT; @@ -636,8 +640,6 @@ __nf_conntrack_confirm(struct sk_buff *skb) zone == nf_ct_zone(nf_ct_tuplehash_to_ctrack(h))) goto out; - nf_ct_del_from_dying_or_unconfirmed_list(ct); - /* Timer relative to confirmation time, not original setting time, otherwise we'd get timer wrap in weird delay cases. */ -- cgit v1.2.3