netfilter: xt_RATEEST: acquire xt_rateest_mutex for hash insert

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>

1 files changed, 17 insertions, 5 deletions

diff --git a/net/netfilter/xt_RATEEST.c b/net/netfilter/xt_RATEEST.c
index 498b54fd04d7..141c295191f6 100644
--- a/net/netfilter/xt_RATEEST.c
+++ b/net/netfilter/xt_RATEEST.c
@@ -39,23 +39,31 @@ static void xt_rateest_hash_insert(struct xt_rateest *est)
         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)
@@ -100,8 +108,10 @@ static int xt_rateest_tg_checkentry(const struct xt_tgchk_param *par)
 
         net_get_random_once(&jhash_rnd, sizeof(jhash_rnd));
 
-        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.
@@ -139,11 +149,13 @@ static int xt_rateest_tg_checkentry(const struct xt_tgchk_param *par)
 
         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;
 }