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    Subject[PATCH 3.18 10/12] NFS: revalidate "." etc correctly on "open".
    Date
    3.18-stable review patch.  If anyone has any objections, please let me know.

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

    From: NeilBrown <neilb@suse.com>

    commit b688741cb06695312f18b730653d6611e1bad28d upstream.

    For correct close-to-open semantics, NFS must validate
    the change attribute of a directory (or file) on open.

    Since commit ecf3d1f1aa74 ("vfs: kill FS_REVAL_DOT by adding a
    d_weak_revalidate dentry op"), open() of "." or a path ending ".." is
    not revalidated reliably (except when that direct is a mount point).

    Prior to that commit, "." was revalidated using nfs_lookup_revalidate()
    which checks the LOOKUP_OPEN flag and forces revalidation if the flag is
    set.
    Since that commit, nfs_weak_revalidate() is used for NFSv3 (which
    ignores the flags) and nothing is used for NFSv4.

    This is fixed by using nfs_lookup_verify_inode() in
    nfs_weak_revalidate(). This does the revalidation exactly when needed.
    Also, add a definition of .d_weak_revalidate for NFSv4.

    The incorrect behavior is easily demonstrated by running "echo *" in
    some non-mountpoint NFS directory while watching network traffic.
    Without this patch, "echo *" sometimes doesn't produce any traffic.
    With the patch it always does.

    Fixes: ecf3d1f1aa74 ("vfs: kill FS_REVAL_DOT by adding a d_weak_revalidate dentry op")
    cc: stable@vger.kernel.org (3.9+)
    Signed-off-by: NeilBrown <neilb@suse.com>
    Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/nfs/dir.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/fs/nfs/dir.c
    +++ b/fs/nfs/dir.c
    @@ -1266,7 +1266,7 @@ static int nfs_weak_revalidate(struct de
    return 0;
    }

    - error = nfs_revalidate_inode(NFS_SERVER(inode), inode);
    + error = nfs_lookup_verify_inode(inode, flags);
    dfprintk(LOOKUPCACHE, "NFS: %s: inode %lu is %s\n",
    __func__, inode->i_ino, error ? "invalid" : "valid");
    return !error;
    @@ -1426,6 +1426,7 @@ static int nfs4_lookup_revalidate(struct

    const struct dentry_operations nfs4_dentry_operations = {
    .d_revalidate = nfs4_lookup_revalidate,
    + .d_weak_revalidate = nfs_weak_revalidate,
    .d_delete = nfs_dentry_delete,
    .d_iput = nfs_dentry_iput,
    .d_automount = nfs_d_automount,

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