The patch below does not apply to the 5.5-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 8c75593c6eee0f661ddf25dfde0e6ad2a84be7a9 Mon Sep 17 00:00:00 2001
From: Trond Myklebust trondmy@gmail.com Date: Thu, 13 Feb 2020 14:51:06 -0500 Subject: [PATCH] NFSv4: Ensure the delegation is pinned in nfs_do_return_delegation()
The call to nfs_do_return_delegation() needs to be taken without any RCU locks. Add a refcount to make sure the delegation remains pinned in memory until we're done.
Fixes: ee05f456772d ("NFSv4: Fix races between open and delegreturn") Signed-off-by: Trond Myklebust trond.myklebust@hammerspace.com Signed-off-by: Anna Schumaker Anna.Schumaker@Netapp.com
diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c index d856326836a2..c17ff826e7e9 100644 --- a/fs/nfs/delegation.c +++ b/fs/nfs/delegation.c @@ -47,10 +47,22 @@ static void nfs_mark_delegation_revoked(struct nfs_delegation *delegation) } }
+static struct nfs_delegation *nfs_get_delegation(struct nfs_delegation *delegation) +{ + refcount_inc(&delegation->refcount); + return delegation; +} + +static void nfs_put_delegation(struct nfs_delegation *delegation) +{ + if (refcount_dec_and_test(&delegation->refcount)) + __nfs_free_delegation(delegation); +} + static void nfs_free_delegation(struct nfs_delegation *delegation) { nfs_mark_delegation_revoked(delegation); - __nfs_free_delegation(delegation); + nfs_put_delegation(delegation); }
/** @@ -275,8 +287,10 @@ nfs_start_delegation_return_locked(struct nfs_inode *nfsi) if (delegation == NULL) goto out; spin_lock(&delegation->lock); - if (!test_and_set_bit(NFS_DELEGATION_RETURNING, &delegation->flags)) - ret = delegation; + if (!test_and_set_bit(NFS_DELEGATION_RETURNING, &delegation->flags)) { + /* Refcount matched in nfs_end_delegation_return() */ + ret = nfs_get_delegation(delegation); + } spin_unlock(&delegation->lock); if (ret) nfs_clear_verifier_delegated(&nfsi->vfs_inode); @@ -397,6 +411,7 @@ int nfs_inode_set_delegation(struct inode *inode, const struct cred *cred, if (delegation == NULL) return -ENOMEM; nfs4_stateid_copy(&delegation->stateid, stateid); + refcount_set(&delegation->refcount, 1); delegation->type = type; delegation->pagemod_limit = pagemod_limit; delegation->change_attr = inode_peek_iversion_raw(inode); @@ -496,6 +511,8 @@ static int nfs_end_delegation_return(struct inode *inode, struct nfs_delegation
err = nfs_do_return_delegation(inode, delegation, issync); out: + /* Refcount matched in nfs_start_delegation_return_locked() */ + nfs_put_delegation(delegation); return err; }
@@ -690,7 +707,8 @@ void nfs4_inode_return_delegation_on_close(struct inode *inode) list_empty(&NFS_I(inode)->open_files) && !test_and_set_bit(NFS_DELEGATION_RETURNING, &delegation->flags)) { clear_bit(NFS_DELEGATION_RETURN_IF_CLOSED, &delegation->flags); - ret = delegation; + /* Refcount matched in nfs_end_delegation_return() */ + ret = nfs_get_delegation(delegation); } spin_unlock(&delegation->lock); if (ret) @@ -1094,10 +1112,11 @@ void nfs_delegation_reap_unclaimed(struct nfs_client *clp) delegation = nfs_start_delegation_return_locked(NFS_I(inode)); rcu_read_unlock(); if (delegation != NULL) { - delegation = nfs_detach_delegation(NFS_I(inode), - delegation, server); - if (delegation != NULL) + if (nfs_detach_delegation(NFS_I(inode), delegation, + server) != NULL) nfs_free_delegation(delegation); + /* Match nfs_start_delegation_return_locked */ + nfs_put_delegation(delegation); } iput(inode); nfs_sb_deactive(server->super); diff --git a/fs/nfs/delegation.h b/fs/nfs/delegation.h index 31b84604d383..9b00a0b7f832 100644 --- a/fs/nfs/delegation.h +++ b/fs/nfs/delegation.h @@ -22,6 +22,7 @@ struct nfs_delegation { unsigned long pagemod_limit; __u64 change_attr; unsigned long flags; + refcount_t refcount; spinlock_t lock; struct rcu_head rcu; };