2020-04-30 19:58:06

by trondmy

[permalink] [raw]
Subject: [PATCH] NFS: Fix a race in __nfs_list_for_each_server()

From: Trond Myklebust <[email protected]>

The struct nfs_server gets put on the cl_superblocks list before
the server->super field has been initialised, in which case the
call to nfs_sb_active() will Oops. Add a check to ensure that
we skip such a list entry.

Fixes: 3c9e502b59fb ("NFS: Add a helper nfs_client_for_each_server()")
Signed-off-by: Trond Myklebust <[email protected]>
---
fs/nfs/super.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 59ef3b13ccca..bdb6d0c2e755 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -185,7 +185,7 @@ static int __nfs_list_for_each_server(struct list_head *head,

rcu_read_lock();
list_for_each_entry_rcu(server, head, client_link) {
- if (!nfs_sb_active(server->super))
+ if (!(server->super && nfs_sb_active(server->super)))
continue;
rcu_read_unlock();
if (last)
--
2.26.2