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    Subject[PATCH 4.8 079/140] NFSv4: nfs4_copy_delegation_stateid() must fail if the delegation is invalid
    Date
    4.8-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Trond Myklebust <trond.myklebust@primarydata.com>

    commit aa05c87f23efe417adc7ff9b4193b7201ec0dd79 upstream.

    We must not allow the use of delegations that have been revoked or are
    being returned.

    Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
    Fixes: 869f9dfa4d6d ("NFSv4: Fix races between nfs_remove_bad_delegation()...")
    Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
    Tested-by: Oleg Drokin <green@linuxhacker.ru>
    Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/nfs/delegation.c | 17 +++++++++++++----
    1 file changed, 13 insertions(+), 4 deletions(-)

    --- a/fs/nfs/delegation.c
    +++ b/fs/nfs/delegation.c
    @@ -41,6 +41,17 @@ void nfs_mark_delegation_referenced(stru
    set_bit(NFS_DELEGATION_REFERENCED, &delegation->flags);
    }

    +static bool
    +nfs4_is_valid_delegation(const struct nfs_delegation *delegation,
    + fmode_t flags)
    +{
    + if (delegation != NULL && (delegation->type & flags) == flags &&
    + !test_bit(NFS_DELEGATION_REVOKED, &delegation->flags) &&
    + !test_bit(NFS_DELEGATION_RETURNING, &delegation->flags))
    + return true;
    + return false;
    +}
    +
    static int
    nfs4_do_check_delegation(struct inode *inode, fmode_t flags, bool mark)
    {
    @@ -50,9 +61,7 @@ nfs4_do_check_delegation(struct inode *i
    flags &= FMODE_READ|FMODE_WRITE;
    rcu_read_lock();
    delegation = rcu_dereference(NFS_I(inode)->delegation);
    - if (delegation != NULL && (delegation->type & flags) == flags &&
    - !test_bit(NFS_DELEGATION_REVOKED, &delegation->flags) &&
    - !test_bit(NFS_DELEGATION_RETURNING, &delegation->flags)) {
    + if (nfs4_is_valid_delegation(delegation, flags)) {
    if (mark)
    nfs_mark_delegation_referenced(delegation);
    ret = 1;
    @@ -894,7 +903,7 @@ bool nfs4_copy_delegation_stateid(struct
    flags &= FMODE_READ|FMODE_WRITE;
    rcu_read_lock();
    delegation = rcu_dereference(nfsi->delegation);
    - ret = (delegation != NULL && (delegation->type & flags) == flags);
    + ret = nfs4_is_valid_delegation(delegation, flags);
    if (ret) {
    nfs4_stateid_copy(dst, &delegation->stateid);
    nfs_mark_delegation_referenced(delegation);

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