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Subject[PATCH v2 3/3] net: make net namespace sysctls belong to container's owner
Date
If net namespace is attached to a user namespace let's make container's
root owner of sysctls affecting said network namespace instead of global
root.

This also allows us to clean up net_ctl_permissions() because we do not
need to fudge permissions anymore for the container's owner since it now
owns the objects in question.

Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
fs/proc/proc_sysctl.c | 5 +++++
include/linux/sysctl.h | 4 ++++
net/sysctl_net.c | 29 ++++++++++++++++++++---------
3 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 5e57c3e..28f9085 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -430,6 +430,7 @@ static int sysctl_perm(struct ctl_table_header *head, struct ctl_table *table, i
static struct inode *proc_sys_make_inode(struct super_block *sb,
struct ctl_table_header *head, struct ctl_table *table)
{
+ struct ctl_table_root *root = head->root;
struct inode *inode;
struct proc_inode *ei;

@@ -457,6 +458,10 @@ static struct inode *proc_sys_make_inode(struct super_block *sb,
if (is_empty_dir(head))
make_empty_dir_inode(inode);
}
+
+ if (root->set_ownership)
+ root->set_ownership(head, table, &inode->i_uid, &inode->i_gid);
+
out:
return inode;
}
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index fa7bc29..55bec2f 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -25,6 +25,7 @@
#include <linux/rcupdate.h>
#include <linux/wait.h>
#include <linux/rbtree.h>
+#include <linux/uidgid.h>
#include <uapi/linux/sysctl.h>

/* For the /proc/sys support */
@@ -156,6 +157,9 @@ struct ctl_table_root {
struct ctl_table_set default_set;
struct ctl_table_set *(*lookup)(struct ctl_table_root *root,
struct nsproxy *namespaces);
+ void (*set_ownership)(struct ctl_table_header *head,
+ struct ctl_table *table,
+ kuid_t *uid, kgid_t *gid);
int (*permissions)(struct ctl_table_header *head, struct ctl_table *table);
};

diff --git a/net/sysctl_net.c b/net/sysctl_net.c
index ed98c1f..5bc1a3d 100644
--- a/net/sysctl_net.c
+++ b/net/sysctl_net.c
@@ -42,26 +42,37 @@ static int net_ctl_permissions(struct ctl_table_header *head,
struct ctl_table *table)
{
struct net *net = container_of(head->set, struct net, sysctls);
- kuid_t root_uid = make_kuid(net->user_ns, 0);
- kgid_t root_gid = make_kgid(net->user_ns, 0);

/* Allow network administrator to have same access as root. */
- if (ns_capable(net->user_ns, CAP_NET_ADMIN) ||
- uid_eq(root_uid, current_euid())) {
+ if (ns_capable(net->user_ns, CAP_NET_ADMIN)) {
int mode = (table->mode >> 6) & 7;
return (mode << 6) | (mode << 3) | mode;
}
- /* Allow netns root group to have the same access as the root group */
- if (in_egroup_p(root_gid)) {
- int mode = (table->mode >> 3) & 7;
- return (mode << 3) | mode;
- }
+
return table->mode;
}

+static void net_ctl_set_ownership(struct ctl_table_header *head,
+ struct ctl_table *table,
+ kuid_t *uid, kgid_t *gid)
+{
+ struct net *net = container_of(head->set, struct net, sysctls);
+ kuid_t ns_root_uid;
+ kgid_t ns_root_gid;
+
+ ns_root_uid = make_kuid(net->user_ns, 0);
+ if (uid_valid(ns_root_uid))
+ *uid = ns_root_uid;
+
+ ns_root_gid = make_kgid(net->user_ns, 0);
+ if (gid_valid(ns_root_gid))
+ *gid = ns_root_gid;
+}
+
static struct ctl_table_root net_sysctl_root = {
.lookup = net_ctl_header_lookup,
.permissions = net_ctl_permissions,
+ .set_ownership = net_ctl_set_ownership,
};

static int __net_init sysctl_net_init(struct net *net)
--
2.8.0.rc3.226.g39d4020
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