netfilter: xt_RATEEST: acquire xt_rateest_mutex for hash insert

Web:        https://git.kernel.org/torvalds/c/7dc68e98757a8eccf8ca7a53a29b896f1eef1f76
Commit:     7dc68e98757a8eccf8ca7a53a29b896f1eef1f76
Parent:     992cfc7c5d105094da7c21c9c74d97ac26bb1e56
Refname:    refs/heads/master
Author:     Cong Wang <[email protected]>
AuthorDate: Mon Feb 5 14:41:45 2018 -0800
Committer:  Pablo Neira Ayuso <[email protected]>
CommitDate: Wed Feb 7 00:58:57 2018 +0100

    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: <[email protected]>
    Fixes: 5859034d7eb8 ("[NETFILTER]: x_tables: add RATEEST target")
    Signed-off-by: Cong Wang <[email protected]>
    Reviewed-by: Florian Westphal <[email protected]>
    Reviewed-by: Eric Dumazet <[email protected]>
    Signed-off-by: Pablo Neira Ayuso <[email protected]>
---
 net/netfilter/xt_RATEEST.c | 22 +++++++++++++++++-----
 1 file 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;
 }
 
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