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Subject[PATCH 4.4 019/193] netfilter: xt_RATEEST: acquire xt_rateest_mutex for hash insert
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Cong Wang <xiyou.wangcong@gmail.com>

commit 7dc68e98757a8eccf8ca7a53a29b896f1eef1f76 upstream.

rateest_hash is supposed to be protected by xt_rateest_mutex,
and, as suggested by Eric, lookup and insert should be atomic,
so we should acquire the xt_rateest_mutex once for both.

So introduce a non-locking helper for internal use and keep the
locking one for external.

Reported-by: <syzbot+5cb189720978275e4c75@syzkaller.appspotmail.com>
Fixes: 5859034d7eb8 ("[NETFILTER]: x_tables: add RATEEST target")
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Reviewed-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/netfilter/xt_RATEEST.c | 22 +++++++++++++++++-----
1 file changed, 17 insertions(+), 5 deletions(-)

--- a/net/netfilter/xt_RATEEST.c
+++ b/net/netfilter/xt_RATEEST.c
@@ -40,23 +40,31 @@ static void xt_rateest_hash_insert(struc
hlist_add_head(&est->list, &rateest_hash[h]);
}

-struct xt_rateest *xt_rateest_lookup(const char *name)
+static struct xt_rateest *__xt_rateest_lookup(const char *name)
{
struct xt_rateest *est;
unsigned int h;

h = xt_rateest_hash(name);
- mutex_lock(&xt_rateest_mutex);
hlist_for_each_entry(est, &rateest_hash[h], list) {
if (strcmp(est->name, name) == 0) {
est->refcnt++;
- mutex_unlock(&xt_rateest_mutex);
return est;
}
}
- mutex_unlock(&xt_rateest_mutex);
+
return NULL;
}
+
+struct xt_rateest *xt_rateest_lookup(const char *name)
+{
+ struct xt_rateest *est;
+
+ mutex_lock(&xt_rateest_mutex);
+ est = __xt_rateest_lookup(name);
+ mutex_unlock(&xt_rateest_mutex);
+ return est;
+}
EXPORT_SYMBOL_GPL(xt_rateest_lookup);

void xt_rateest_put(struct xt_rateest *est)
@@ -104,8 +112,10 @@ static int xt_rateest_tg_checkentry(cons
rnd_inited = true;
}

- est = xt_rateest_lookup(info->name);
+ mutex_lock(&xt_rateest_mutex);
+ est = __xt_rateest_lookup(info->name);
if (est) {
+ mutex_unlock(&xt_rateest_mutex);
/*
* If estimator parameters are specified, they must match the
* existing estimator.
@@ -143,11 +153,13 @@ static int xt_rateest_tg_checkentry(cons

info->est = est;
xt_rateest_hash_insert(est);
+ mutex_unlock(&xt_rateest_mutex);
return 0;

err2:
kfree(est);
err1:
+ mutex_unlock(&xt_rateest_mutex);
return ret;
}


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