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authorbill bonaparte <programme110@gmail.com>2014-11-06 14:36:48 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-12-06 15:57:34 -0800
commit88fd8709858b9cd94e2d28b4b3cac4b752f0683a (patch)
tree78559d8e2c21ae2b97605309aeb7776020cf93d1
parent2b385019adf661fa20ae263103096acc4e05447d (diff)
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 <programme110@gmail.com> Signed-off-by: bill bonaparte <programme110@gmail.com> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--net/netfilter/nf_conntrack_core.c14
1 files 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. */