NFS: Beware when dereferencing the delegation cred
When we look up the delegation cred, we are usually doing so in
conjunction with a read of the stateid, and we want to ensure
that the look up is atomic with that read.
Fixes: 57f188e04773 ("NFSv4: nfs_update_inplace_delegation() should update delegation cred")
[sfr@canb.auug.org.au: Fixed up borken Fixes: line from Trond :-)]
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 905c7d1..e4f8311 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2790,16 +2790,19 @@ static int nfs41_check_delegation_stateid(struct nfs4_state *state)
return NFS_OK;
}
+ spin_lock(&delegation->lock);
nfs4_stateid_copy(&stateid, &delegation->stateid);
if (!test_and_clear_bit(NFS_DELEGATION_TEST_EXPIRED,
&delegation->flags)) {
+ spin_unlock(&delegation->lock);
rcu_read_unlock();
return NFS_OK;
}
if (delegation->cred)
cred = get_cred(delegation->cred);
+ spin_unlock(&delegation->lock);
rcu_read_unlock();
status = nfs41_test_and_free_expired_stateid(server, &stateid, cred);
trace_nfs4_test_delegation_stateid(state, NULL, status);