From: Trond Myklebust trond.myklebust@hammerspace.com

hulk inclusion category: bugfix bugzilla: 51898 CVE: NA

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If the inode is being evicted, but has to return a delegation first, then it can cause a deadlock in the corner case where the server reboots before the delegreturn completes, but while the call to iget5_locked() in nfs4_opendata_get_inode() is waiting for the inode free to complete. Since the open call still holds a session slot, the reboot recovery cannot proceed.

In order to break the logjam, we can turn the delegation return into a privileged operation for the case where we're evicting the inode. We know that in that case, there can be no other state recovery operation that conflicts.

Reported-by: zhangxiaoxu (A) zhangxiaoxu5@huawei.com Fixes: 5fcdfacc01f3 ("NFSv4: Return delegations synchronously in evict_inode") Signed-off-by: Trond Myklebust trond.myklebust@hammerspace.com

Link: https://patchwork.kernel.org/project/linux-nfs/list/?series=491989 Conflict: fs/nfs/nfs4proc.c Signed-off-by: Zhang Xiaoxu zhangxiaoxu5@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- fs/nfs/nfs4_fs.h | 1 + fs/nfs/nfs4proc.c | 13 ++++++++++++- 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h index a6b0b544c82d9..4f3b5add052b8 100644 --- a/fs/nfs/nfs4_fs.h +++ b/fs/nfs/nfs4_fs.h @@ -201,6 +201,7 @@ struct nfs4_exception { struct inode *inode; nfs4_stateid *stateid; long timeout; + unsigned char task_is_privileged : 1; unsigned char delay : 1, recovering : 1, retry : 1; diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index 35a60c3ed023f..5d9c132ffd760 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -564,6 +564,8 @@ int nfs4_handle_exception(struct nfs_server *server, int errorcode, struct nfs4_ goto out_retry; } if (exception->recovering) { + if (exception->task_is_privileged) + return -EDEADLOCK; ret = nfs4_wait_clnt_recover(clp); if (test_bit(NFS_MIG_FAILED, &server->mig_status)) return -EIO; @@ -589,6 +591,8 @@ nfs4_async_handle_exception(struct rpc_task *task, struct nfs_server *server, goto out_retry; } if (exception->recovering) { + if (exception->task_is_privileged) + return -EDEADLOCK; rpc_sleep_on(&clp->cl_rpcwaitq, task, NULL); if (test_bit(NFS4CLNT_MANAGER_RUNNING, &clp->cl_state) == 0) rpc_wake_up_queued_task(&clp->cl_rpcwaitq, task); @@ -6102,6 +6106,7 @@ static void nfs4_delegreturn_done(struct rpc_task *task, void *calldata) struct nfs4_exception exception = { .inode = data->inode, .stateid = &data->stateid, + .task_is_privileged = data->args.seq_args.sa_privileged, };

if (!nfs4_sequence_done(task, &data->res.seq_res)) @@ -6246,7 +6251,6 @@ static int _nfs4_proc_delegreturn(struct inode *inode, struct rpc_cred *cred, co data = kzalloc(sizeof(*data), GFP_NOFS); if (data == NULL) return -ENOMEM; - nfs4_init_sequence(&data->args.seq_args, &data->res.seq_res, 1, 0);

nfs4_state_protect(server->nfs_client, NFS_SP4_MACH_CRED_CLEANUP, @@ -6276,6 +6280,13 @@ static int _nfs4_proc_delegreturn(struct inode *inode, struct rpc_cred *cred, co data->lr.roc = false; }

+ if (!data->inode) + nfs4_init_sequence(&data->args.seq_args, &data->res.seq_res, 1, + 1); + else + nfs4_init_sequence(&data->args.seq_args, &data->res.seq_res, 1, + 0); + task_setup_data.callback_data = data; msg.rpc_argp = &data->args; msg.rpc_resp = &data->res;