From: bill bonaparte <programme110@xxxxxxxxx>
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.
Fixes: 93bb0ceb75be2 ("netfilter: conntrack: remove central spinlock nf_conntrack_lock")
Reported-by: bill bonaparte <programme110@xxxxxxxxx>
Signed-off-by: bill bonaparte <programme110@xxxxxxxxx>
Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
---
net/netfilter/nf_conntrack_core.c | 7 ++++---
1 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 5016a69..1072650 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -611,12 +611,15 @@ __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
+
+ /* 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 +639,6 @@ __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. */
--
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