[PATCH] Fix suspicious RCU usage in nfs_idmap_get_key.

[Artem Savkov]

nfs_idmap_get_key doesn't hold rkey->sem when calling user_key_payload
resulting in a "suspicious RCU usage" lockdep splat. It does, however 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 <asav...@redhat.com>
---
 fs/nfs/nfs4idmap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/nfs4idmap.c b/fs/nfs/nfs4idmap.c
index c444285..a67d1c0 100644
--- a/fs/nfs/nfs4idmap.c
+++ b/fs/nfs/nfs4idmap.c
@@ -309,7 +309,7 @@ static ssize_t nfs_idmap_get_key(const char *name, size_t 
namelen,
                goto out;
        }
 
-       rcu_read_lock();
+       down_read(&rkey->sem);
        rkey->perm |= KEY_USR_VIEW;
 
        ret = key_validate(rkey);
@@ -329,7 +329,7 @@ static ssize_t nfs_idmap_get_key(const char *name, size_t 
namelen,
                ret = -EINVAL;
 
 out_up:
-       rcu_read_unlock();
+       up_read(&rkey->sem);
        key_put(rkey);
 out:
        return ret;
-- 
2.7.4