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netfilter: xt_recent: Fix attempt to update deleted entry

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When both --reap and --update flag are specified, there's a code
path at which the entry to be updated is reaped beforehand,
which then leads to kernel crash. Reap only entries which won't be
updated.

Fixes kernel bugzilla #207773.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=207773
Reported-by: Reindl Harald <h.reindl@thelounge.net>
Fixes: 0079c5aee3 ("netfilter: xt_recent: add an entry reaper")
Signed-off-by: Jozsef Kadlecsik <kadlec@netfilter.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Jozsef Kadlecsik 2021-01-29 20:57:43 +01:00 committed by Pablo Neira Ayuso
parent 44a674d6f7
commit b1bdde33b7
1 changed files with 10 additions and 2 deletions
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12
net/netfilter/xt_recent.c
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@ -152,7 +152,8 @@ static void recent_entry_remove(struct recent_table *t, struct recent_entry *e)
/*
* Drop entries with timestamps older then 'time'.
*/
static void recent_entry_reap(struct recent_table *t, unsigned long time)
static void recent_entry_reap(struct recent_table *t, unsigned long time,
struct recent_entry *working, bool update)
{
struct recent_entry *e;
@ -161,6 +162,12 @@ static void recent_entry_reap(struct recent_table *t, unsigned long time)
*/
e = list_entry(t->lru_list.next, struct recent_entry, lru_list);
/*
* Do not reap the entry which are going to be updated.
*/
if (e == working && update)
return;
/*
* The last time stamp is the most recent.
*/
@ -303,7 +310,8 @@ recent_mt(const struct sk_buff *skb, struct xt_action_param *par)
/* info->seconds must be non-zero */
if (info->check_set & XT_RECENT_REAP)
recent_entry_reap(t, time);
recent_entry_reap(t, time, e,
info->check_set & XT_RECENT_UPDATE && ret);
}
if (info->check_set & XT_RECENT_SET ||