[PATCH] NFS: Fix an rcu deadlock in nfs_delegation_find_inode()

* [PATCH] NFS: Fix an rcu deadlock in nfs_delegation_find_inode()
@ 2018-06-14 13:39 schumaker.anna
  2018-06-14 16:26 ` Trond Myklebust
  0 siblings, 1 reply; 2+ messages in thread
From: schumaker.anna @ 2018-06-14 13:39 UTC (permalink / raw)
  To: Trond.Myklebust, linux-nfs; +Cc: ross.zwisler

From: Anna Schumaker <Anna.Schumaker@Netapp.com>

I was able to reproduce this pretty regularily using xfstests
generic/013 on NFS v4.0.

Reported-by: Ross Zwisler <Ross.Zwisler@linux.intel.com>
Fixes: a337fe91 (NFSv4: Return NFS4ERR_DELAY when a delegation recall fails due to igrab())
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
---
 fs/nfs/delegation.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index bbd0465535eb..f033f3a69a3b 100644
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -883,8 +883,10 @@ struct inode *nfs_delegation_find_inode(struct nfs_client *clp,
 	rcu_read_lock();
 	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
 		res = nfs_delegation_find_inode_server(server, fhandle);
-		if (res != ERR_PTR(-ENOENT))
+		if (res != ERR_PTR(-ENOENT)) {
+			rcu_read_unlock();
 			return res;
+		}
 	}
 	rcu_read_unlock();
 	return ERR_PTR(-ENOENT);
-- 
2.17.1


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