This patch provides a netlink interaface for the namespace filesystem list.
It is quite simple, and I need at least one more operation (query).
Also, keep in mind that although I wrote it believing it is a nice
interface to manipulate the list, I don't feel strongly about the
interface per-se. So feel free to suggest something better.
Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
---
fs/Kconfig | 9 +++
fs/Makefile | 1 +
fs/fsnetlink.c | 145 ++++++++++++++++++++++++++++++++++++++++
include/linux/fslist_netlink.h | 35 ++++++++++
4 files changed, 190 insertions(+), 0 deletions(-)
create mode 100644 fs/fsnetlink.c
create mode 100644 include/linux/fslist_netlink.h
diff --git a/fs/Kconfig b/fs/Kconfig
index 440d189..842dcc4 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -78,6 +78,15 @@ config GENERIC_ACL
bool
select FS_POSIX_ACL
+config FSLIST_NETLINK
+ bool "Filesystem Lists Netlink"
+ help
+ This option allows userspace to select a sublist of the available
+ filesystems that are mountable by a particular namespace. It provides
+ a netlink interface through which one can manage such a set.
+
+
+
menu "Caches"
source "fs/fscache/Kconfig"
diff --git a/fs/Makefile b/fs/Makefile
index 57d446d..675f613 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -46,6 +46,7 @@ obj-$(CONFIG_FS_MBCACHE) += mbcache.o
obj-$(CONFIG_FS_POSIX_ACL) += posix_acl.o xattr_acl.o
obj-$(CONFIG_NFS_COMMON) += nfs_common/
obj-$(CONFIG_GENERIC_ACL) += generic_acl.o
+obj-$(CONFIG_FSLIST_NETLINK) += fsnetlink.o
obj-$(CONFIG_FHANDLE) += fhandle.o
diff --git a/fs/fsnetlink.c b/fs/fsnetlink.c
new file mode 100644
index 0000000..619fad1
--- /dev/null
+++ b/fs/fsnetlink.c
@@ -0,0 +1,145 @@
+#include <net/genetlink.h>
+#include <linux/fslist_netlink.h>
+#include <linux/gfp.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/nsproxy.h>
+#include <linux/mnt_namespace.h>
+#include <linux/fs_struct.h>
+#include <linux/dcache.h>
+
+static struct nla_policy fslist_genl_policy[FSLIST_A_MAX + 1] = {
+ [FSLIST_A_OP] = { .type = NLA_U32 },
+ [FSLIST_A_OP_ARG] = { .type = NLA_STRING, .len = 200 },
+};
+
+static struct genl_family fslist_gnl_family = {
+ .id = GENL_ID_GENERATE,
+ .name = FSLIST_GENL_NAME,
+ .version = FSLIST_GENL_VERSION,
+ .maxattr = FSLIST_A_MAX,
+};
+
+static int msg_reply(int ret, struct genl_info *info)
+{
+ struct sk_buff *skb;
+ void *reply;
+ size_t size;
+ struct genlmsghdr *genlhdr;
+ void *data;
+
+ size = nla_total_size(1) +
+ nla_total_size(0);
+
+ skb = genlmsg_new(size, GFP_KERNEL);
+ if (!skb)
+ return -ENOMEM;
+
+ reply = genlmsg_put_reply(skb, info, &fslist_gnl_family, 0, FSLIST_CMD_REPLY);
+ if (reply == NULL) {
+ nlmsg_free(skb);
+ return -EINVAL;
+ }
+
+ nla_put_u32(skb, FSLIST_A_OP, ret);
+
+ genlhdr = nlmsg_data((struct nlmsghdr *)skb->data);
+ data = genlmsg_data(genlhdr);
+
+ ret = genlmsg_end(skb, data);
+ if (ret < 0) {
+ nlmsg_free(skb);
+ return ret;
+ }
+
+ return genlmsg_reply(skb, info);
+}
+
+
+static int cmd_ask(struct sk_buff *skb, struct genl_info *info)
+{
+ struct nlattr *na;
+ int op = 0;
+ char *data = NULL;
+ int ret = 0;
+ struct mnt_namespace *mnt = current->nsproxy->mnt_ns;
+ struct dentry *curr_root;
+ int msg_ret = 0;
+
+ /*
+ * Once a process is contained by a chroot environment,
+ * we don't allow the list to grow further, or be by
+ * any means modified.
+ *
+ * It should still work after pivot_root, though.
+ */
+ curr_root = current->fs->root.dentry;
+ if (curr_root->d_parent != curr_root)
+ return -EINVAL;
+
+ na = info->attrs[FSLIST_A_OP];
+ if (na)
+ op = nla_get_u32(na);
+
+ na = info->attrs[FSLIST_A_OP_ARG];
+ if (na) {
+ int len = nla_len(na);
+
+ data = kmalloc(len, GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ nla_strlcpy(data, na, len);
+ }
+
+ switch (op) {
+ case FSLIST_OP_RESET:
+ enable_filesystems_list(mnt);
+ break;
+ case FSLIST_OP_ADD:
+ if (!data) {
+ ret = -EINVAL;
+ break;
+ }
+ msg_ret = add_filesystem_list(data, mnt);
+ break;
+ case FSLIST_OP_QUERY:
+ ret = -ENOSYS;
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ }
+
+ kfree(data);
+ if (!ret)
+ msg_reply(msg_ret, info);
+ return ret;
+}
+
+static struct genl_ops fslist_nl_ops = {
+ .cmd = FSLIST_CMD_ASK,
+ .doit = cmd_ask,
+ .policy = fslist_genl_policy,
+};
+
+int __init fslist_netlink_init(void)
+{
+ int ret;
+ ret = genl_register_family(&fslist_gnl_family);
+ if (ret)
+ return ret;
+
+ ret = genl_register_ops(&fslist_gnl_family, &fslist_nl_ops);
+ if (ret)
+ goto fail_unregister;
+
+ return 0;
+
+fail_unregister:
+ genl_unregister_family(&fslist_gnl_family);
+ return ret;
+}
+
+fs_initcall(fslist_netlink_init);
+
diff --git a/include/linux/fslist_netlink.h b/include/linux/fslist_netlink.h
new file mode 100644
index 0000000..926760d
--- /dev/null
+++ b/include/linux/fslist_netlink.h
@@ -0,0 +1,35 @@
+#ifndef _FSLIST_NETLINK_H
+#define _FSLIST_NETLINK_H
+
+#ifdef __KERNEL__
+#include <linux/types.h>
+#endif
+
+enum {
+ FSLIST_A_UNSPEC,
+ FSLIST_A_OP,
+ FSLIST_A_OP_ARG,
+ __FSLIST_A_MAX,
+};
+
+#define FSLIST_A_MAX (__FSLIST_A_MAX - 1)
+
+enum {
+ FSLIST_CMD_UNSPEC = 0,
+ FSLIST_CMD_ASK, /* user->kernel */
+ FSLIST_CMD_REPLY, /* kernel->user */
+ __FSLIST_CMD_MAX,
+};
+
+#define FSLIST_CMD_MAX (__FSLIST_CMD_MAX - 1)
+
+#define FSLIST_GENL_VERSION 0x1
+#define FSLIST_GENL_NAME "FSLIST"
+
+enum {
+ FSLIST_OP_RESET = 1,
+ FSLIST_OP_ADD,
+ FSLIST_OP_QUERY,
+};
+
+#endif /* _FSLIST_NETLINK_H */
--
1.7.7.4
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