When remounting an NFS or NFS4 filesystem, the new NFS options are not
respected, yet the remount will still return success. This patch adds
a remount_fs sb op for NFS that checks any new nfs mount options against
the existing ones and fails the mount if any have changed.
This is only implemented for string-based mount options since doing
this with binary options isn't really feasible.
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
fs/nfs/super.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 70 insertions(+), 0 deletions(-)
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index f4ee9d9..b49f90f 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -207,6 +207,7 @@ static int nfs_xdev_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt);
static void nfs_kill_super(struct super_block *);
static void nfs_put_super(struct super_block *);
+static int nfs_remount(struct super_block *sb, int *flags, char *raw_data);
static struct file_system_type nfs_fs_type = {
.owner = THIS_MODULE,
@@ -234,6 +235,7 @@ static const struct super_operations nfs_sops = {
.umount_begin = nfs_umount_begin,
.show_options = nfs_show_options,
.show_stats = nfs_show_stats,
+ .remount_fs = nfs_remount,
};
#ifdef CONFIG_NFS_V4
@@ -278,6 +280,7 @@ static const struct super_operations nfs4_sops = {
.umount_begin = nfs_umount_begin,
.show_options = nfs_show_options,
.show_stats = nfs_show_stats,
+ .remount_fs = nfs_remount,
};
#endif
@@ -1327,6 +1330,73 @@ out_invalid_fh:
return -EINVAL;
}
+static int
+nfs_compare_remount_data(struct nfs_server *nfss,
+ struct nfs_parsed_mount_data *data)
+{
+ if (data->flags != nfss->flags ||
+ data->rsize != nfss->rsize ||
+ data->wsize != nfss->wsize ||
+ data->retrans != nfss->client->cl_timeout->to_retries ||
+ data->auth_flavors[0] != nfss->client->cl_auth->au_flavor ||
+ data->acregmin != nfss->acregmin / HZ ||
+ data->acregmax != nfss->acregmax / HZ ||
+ data->acdirmin != nfss->acdirmin / HZ ||
+ data->acdirmax != nfss->acdirmax / HZ ||
+ data->timeo != (10U * nfss->client->cl_timeout->to_initval / HZ))
+ return -EINVAL;
+ else
+ return 0;
+}
+
+static int
+nfs_remount(struct super_block *sb, int *flags, char *raw_data)
+{
+ int error;
+ struct nfs_server *nfss = sb->s_fs_info;
+ struct nfs_parsed_mount_data *data;
+ struct nfs_mount_data *options = (struct nfs_mount_data *)raw_data;
+ struct nfs4_mount_data *options4 = (struct nfs4_mount_data *)raw_data;
+
+ /*
+ * Userspace mount programs that send binary options generally send
+ * them populated with default values. We have no way to know which
+ * ones were explicitly specified. Fall back to legacy behavior and
+ * just return success.
+ */
+ if ((sb->s_type == &nfs4_fs_type && options4->version == 1) ||
+ (sb->s_type == &nfs_fs_type && options->version >= 1 &&
+ options->version <= 6))
+ return 0;
+
+ data = kzalloc(sizeof(*data), GFP_KERNEL);
+ if (data == NULL)
+ return -ENOMEM;
+
+ /* fill out struct with values from existing mount */
+ data->flags = nfss->flags;
+ data->rsize = nfss->rsize;
+ data->wsize = nfss->wsize;
+ data->retrans = nfss->client->cl_timeout->to_retries;
+ data->auth_flavors[0] = nfss->client->cl_auth->au_flavor;
+ data->acregmin = nfss->acregmin / HZ;
+ data->acregmax = nfss->acregmax / HZ;
+ data->acdirmin = nfss->acdirmin / HZ;
+ data->acdirmax = nfss->acdirmax / HZ;
+ data->timeo = 10U * nfss->client->cl_timeout->to_initval / HZ;
+
+ /* overwrite those values with any that were specified */
+ error = nfs_parse_mount_options((char *)options, data);
+ if (error < 0)
+ goto out;
+
+ /* compare new mount options with old ones */
+ error = nfs_compare_remount_data(nfss, data);
+out:
+ kfree(data);
+ return error;
+}
+
/*
* Initialise the common bits of the superblock
*/
--
1.5.3.6
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