From fc51b1cf391dd91ff9362861ed226ef51048e863 Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Thu, 2 Apr 2020 15:27:09 -0400 Subject: NFS: Beware when dereferencing the delegation cred When we look up the delegation cred, we are usually doing so in conjunction with a read of the stateid, and we want to ensure that the look up is atomic with that read. Fixes: 57f188e04773 ("NFSv4: nfs_update_inplace_delegation() should update delegation cred") [sfr@canb.auug.org.au: Fixed up borken Fixes: line from Trond :-)] Signed-off-by: Trond Myklebust --- fs/nfs/delegation.c | 9 ++++++++- fs/nfs/nfs4proc.c | 3 +++ 2 files changed, 11 insertions(+), 1 deletion(-) (limited to 'fs') diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c index 01974f17afc9..816e1427f17e 100644 --- a/fs/nfs/delegation.c +++ b/fs/nfs/delegation.c @@ -1243,8 +1243,10 @@ restart_locked: inode = nfs_delegation_grab_inode(delegation); if (inode == NULL) goto restart_locked; + spin_lock(&delegation->lock); cred = get_cred_rcu(delegation->cred); nfs4_stateid_copy(&stateid, &delegation->stateid); + spin_unlock(&delegation->lock); clear_bit(NFS_DELEGATION_TEST_EXPIRED, &delegation->flags); rcu_read_unlock(); nfs_delegation_test_free_expired(inode, &stateid, cred); @@ -1363,11 +1365,14 @@ bool nfs4_copy_delegation_stateid(struct inode *inode, fmode_t flags, { struct nfs_inode *nfsi = NFS_I(inode); struct nfs_delegation *delegation; - bool ret; + bool ret = false; flags &= FMODE_READ|FMODE_WRITE; rcu_read_lock(); delegation = rcu_dereference(nfsi->delegation); + if (!delegation) + goto out; + spin_lock(&delegation->lock); ret = nfs4_is_valid_delegation(delegation, flags); if (ret) { nfs4_stateid_copy(dst, &delegation->stateid); @@ -1375,6 +1380,8 @@ bool nfs4_copy_delegation_stateid(struct inode *inode, fmode_t flags, if (cred) *cred = get_cred(delegation->cred); } + spin_unlock(&delegation->lock); +out: rcu_read_unlock(); return ret; } diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index 905c7d1bc277..e4f8311e506c 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -2790,16 +2790,19 @@ static int nfs41_check_delegation_stateid(struct nfs4_state *state) return NFS_OK; } + spin_lock(&delegation->lock); nfs4_stateid_copy(&stateid, &delegation->stateid); if (!test_and_clear_bit(NFS_DELEGATION_TEST_EXPIRED, &delegation->flags)) { + spin_unlock(&delegation->lock); rcu_read_unlock(); return NFS_OK; } if (delegation->cred) cred = get_cred(delegation->cred); + spin_unlock(&delegation->lock); rcu_read_unlock(); status = nfs41_test_and_free_expired_stateid(server, &stateid, cred); trace_nfs4_test_delegation_stateid(state, NULL, status); -- cgit v1.2.3