linux-kernel - [PATCH] Use proper lock in fscache_objlist

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Message-Id: <1475588310-10910-1-git-send-email-asavkov@redhat.com>
Date:   Tue,  4 Oct 2016 15:38:30 +0200
From:   Artem Savkov <asavkov@...hat.com>
To:     dhowells@...hat.com
Cc:     linux-cachefs@...hat.com, linux-kernel@...r.kernel.org,
        Artem Savkov <asavkov@...hat.com>
Subject: [PATCH] Use proper lock in fscache_objlist_config.

fscache_objlist_config doesn't hold rkey->sem when calling user_key_payload,
that can result in a "suspicious RCU usage" warning. It does hold
rcu_read_lock,  so it either needs to use unprotected rcu_dereference,
or take rkey->sem instead of rcu_read_lock.

Signed-off-by: Artem Savkov <asavkov@...hat.com>
---
 fs/fscache/object-list.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/fscache/object-list.c b/fs/fscache/object-list.c
index 5d5ddaa..26c20e9 100644
--- a/fs/fscache/object-list.c
+++ b/fs/fscache/object-list.c
@@ -327,7 +327,7 @@ static void fscache_objlist_config(struct fscache_objlist_data *data)
 		goto no_config;
 
 	config = 0;
-	rcu_read_lock();
+	down_read(&key->sem);
 
 	confkey = user_key_payload(key);
 	buf = confkey->data;
@@ -349,7 +349,7 @@ static void fscache_objlist_config(struct fscache_objlist_data *data)
 		}
 	}
 
-	rcu_read_unlock();
+	up_read(&key->sem);
 	key_put(key);
 
 	if (!(config & (FSCACHE_OBJLIST_CONFIG_COOKIE | FSCACHE_OBJLIST_CONFIG_NOCOOKIE)))
-- 
2.7.4