[PATCH] NFSv4: fix a mount deadlock in NFS v4.1 client

Oleksandr Tymoshenko
2024-09-06T00:57:23Z

nfs41_init_clientid does not signal a failure condition from
nfs4_proc_exchange_id and nfs4_proc_create_session to a client which may
lead to mount syscall indefinitely blocked in the following stack trace:
nfs_wait_client_init_complete
nfs41_discover_server_trunking
nfs4_discover_server_trunking
nfs4_init_client
nfs4_set_client
nfs4_create_server
nfs4_try_get_tree
vfs_get_tree
do_new_mount
__se_sys_mount

and the client stuck in uninitialized state.

In addition to this all subsequent mount calls would also get blocked in
nfs_match_client waiting for the uninitialized client to finish
initialization:
nfs_wait_client_init_complete
nfs_match_client
nfs_get_client
nfs4_set_client
nfs4_create_server
nfs4_try_get_tree
vfs_get_tree
do_new_mount
__se_sys_mount

To avoid this situation propagate error condition to the mount thread
and let mount syscall fail properly.

Signed-off-by: Oleksandr Tymoshenko <ovt@google.com>
---
fs/nfs/nfs4state.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 877f682b45f2..54ad3440ad2b 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -335,8 +335,8 @@ int nfs41_init_clientid(struct nfs_client *clp, const struct cred *cred)
if (!(clp->cl_exchange_flags & EXCHGID4_FLAG_CONFIRMED_R))
nfs4_state_start_reclaim_reboot(clp);
nfs41_finish_session_reset(clp);
- nfs_mark_client_ready(clp, NFS_CS_READY);
out:
+ nfs_mark_client_ready(clp, status == 0 ? NFS_CS_READY : status);
return status;
}

---
base-commit: ad618736883b8970f66af799e34007475fe33a68
change-id: 20240906-nfs-mount-deadlock-fix-55c14b38e088

Best regards,
--
Oleksandr Tymoshenko <ovt@google.com>