From 65f2a5c366353da6fa724c68347e1de954928143 Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Thu, 3 Oct 2024 15:34:58 -0400 Subject: [PATCH] nfs_common: fix race in NFS calls to nfsd_file_put_local() and nfsd_serv_put() Add nfs_to_nfsd_file_put_local() interface to fix race with nfsd module unload. Similarly, use RCU around nfs_open_local_fh()'s error path call to nfs_to->nfsd_serv_put(). Holding RCU ensures that NFS will safely _call and return_ from its nfs_to calls into the NFSD functions nfsd_file_put_local() and nfsd_serv_put(). Otherwise, if RCU isn't used then there is a narrow window when NFS's reference for the nfsd_file and nfsd_serv are dropped and the NFSD module could be unloaded, which could result in a crash from the return instruction for either nfs_to->nfsd_file_put_local() or nfs_to->nfsd_serv_put(). Reported-by: NeilBrown Signed-off-by: Mike Snitzer Signed-off-by: Anna Schumaker --- fs/nfs/localio.c | 6 +++--- fs/nfs_common/nfslocalio.c | 5 ++++- fs/nfsd/filecache.c | 2 +- fs/nfsd/localio.c | 2 +- fs/nfsd/nfssvc.c | 4 ++-- include/linux/nfslocalio.h | 15 +++++++++++++++ 6 files changed, 26 insertions(+), 8 deletions(-) diff --git a/fs/nfs/localio.c b/fs/nfs/localio.c index c5922b1a77c0..d0aa680ec816 100644 --- a/fs/nfs/localio.c +++ b/fs/nfs/localio.c @@ -340,7 +340,7 @@ nfs_local_pgio_release(struct nfs_local_kiocb *iocb) { struct nfs_pgio_header *hdr = iocb->hdr; - nfs_to->nfsd_file_put_local(iocb->localio); + nfs_to_nfsd_file_put_local(iocb->localio); nfs_local_iocb_free(iocb); nfs_local_hdr_release(hdr, hdr->task.tk_ops); } @@ -621,7 +621,7 @@ int nfs_local_doio(struct nfs_client *clp, struct nfsd_file *localio, } out: if (status != 0) { - nfs_to->nfsd_file_put_local(localio); + nfs_to_nfsd_file_put_local(localio); hdr->task.tk_status = status; nfs_local_hdr_release(hdr, call_ops); } @@ -672,7 +672,7 @@ nfs_local_release_commit_data(struct nfsd_file *localio, struct nfs_commit_data *data, const struct rpc_call_ops *call_ops) { - nfs_to->nfsd_file_put_local(localio); + nfs_to_nfsd_file_put_local(localio); call_ops->rpc_call_done(&data->task, data); call_ops->rpc_release(data); } diff --git a/fs/nfs_common/nfslocalio.c b/fs/nfs_common/nfslocalio.c index 42b479b9191f..5c8ce5066c16 100644 --- a/fs/nfs_common/nfslocalio.c +++ b/fs/nfs_common/nfslocalio.c @@ -142,8 +142,11 @@ struct nfsd_file *nfs_open_local_fh(nfs_uuid_t *uuid, /* We have an implied reference to net thanks to nfsd_serv_try_get */ localio = nfs_to->nfsd_open_local_fh(net, uuid->dom, rpc_clnt, cred, nfs_fh, fmode); - if (IS_ERR(localio)) + if (IS_ERR(localio)) { + rcu_read_lock(); nfs_to->nfsd_serv_put(net); + rcu_read_unlock(); + } return localio; } EXPORT_SYMBOL_GPL(nfs_open_local_fh); diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index 19bb88c7eebd..53070e1de3d9 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -398,7 +398,7 @@ nfsd_file_put(struct nfsd_file *nf) * reference to the associated nn->nfsd_serv. */ void -nfsd_file_put_local(struct nfsd_file *nf) +nfsd_file_put_local(struct nfsd_file *nf) __must_hold(rcu) { struct net *net = nf->nf_net; diff --git a/fs/nfsd/localio.c b/fs/nfsd/localio.c index 291e9c69cae4..f441cb9f74d5 100644 --- a/fs/nfsd/localio.c +++ b/fs/nfsd/localio.c @@ -53,7 +53,7 @@ void nfsd_localio_ops_init(void) * * On successful return, returned nfsd_file will have its nf_net member * set. Caller (NFS client) is responsible for calling nfsd_serv_put and - * nfsd_file_put (via nfs_to->nfsd_file_put_local). + * nfsd_file_put (via nfs_to_nfsd_file_put_local). */ struct nfsd_file * nfsd_open_local_fh(struct net *net, struct auth_domain *dom, diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c index e236135ddc63..47172b407be8 100644 --- a/fs/nfsd/nfssvc.c +++ b/fs/nfsd/nfssvc.c @@ -214,14 +214,14 @@ int nfsd_minorversion(struct nfsd_net *nn, u32 minorversion, enum vers_op change return 0; } -bool nfsd_serv_try_get(struct net *net) +bool nfsd_serv_try_get(struct net *net) __must_hold(rcu) { struct nfsd_net *nn = net_generic(net, nfsd_net_id); return (nn && percpu_ref_tryget_live(&nn->nfsd_serv_ref)); } -void nfsd_serv_put(struct net *net) +void nfsd_serv_put(struct net *net) __must_hold(rcu) { struct nfsd_net *nn = net_generic(net, nfsd_net_id); diff --git a/include/linux/nfslocalio.h b/include/linux/nfslocalio.h index b353abe00357..b0dd9b1eef4f 100644 --- a/include/linux/nfslocalio.h +++ b/include/linux/nfslocalio.h @@ -65,10 +65,25 @@ struct nfsd_file *nfs_open_local_fh(nfs_uuid_t *, struct rpc_clnt *, const struct cred *, const struct nfs_fh *, const fmode_t); +static inline void nfs_to_nfsd_file_put_local(struct nfsd_file *localio) +{ + /* + * Once reference to nfsd_serv is dropped, NFSD could be + * unloaded, so ensure safe return from nfsd_file_put_local() + * by always taking RCU. + */ + rcu_read_lock(); + nfs_to->nfsd_file_put_local(localio); + rcu_read_unlock(); +} + #else /* CONFIG_NFS_LOCALIO */ static inline void nfsd_localio_ops_init(void) { } +static inline void nfs_to_nfsd_file_put_local(struct nfsd_file *localio) +{ +} #endif /* CONFIG_NFS_LOCALIO */ #endif /* __LINUX_NFSLOCALIO_H */