Re: [PATCH v2 3/3] net: make net namespace sysctls belong to container's owner
From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Date: 2016-09-29 15:46:17
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Hi David, On Wed, Aug 10, 2016 at 2:36 PM, Dmitry Torokhov [off-list ref] wrote:
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" <redacted> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
I was looking at linux-next today, and I noticed that, when you merged
my patch, you basically reverted the following commit:
commit d6e0d306449bcb5fa3c80e7a3edf11d45abf9ae9
Author: Tyler Hicks [off-list ref]
Date: Thu Jun 2 23:43:22 2016 -0500
net: Use ns_capable_noaudit() when determining net sysctl permissions
The capability check should not be audited since it is only being used
to determine the inode permissions. A failed check does not indicate a
violation of security policy but, when an LSM is enabled, a denial audit
message was being generated.
The denial audit message caused confusion for some application authors
because root-running Go applications always triggered the denial. To
prevent this confusion, the capability check in net_ctl_permissions() is
switched to the noaudit variant.
BugLink: https://launchpad.net/bugs/1465724
Signed-off-by: Tyler Hicks [off-list ref]
Acked-by: Serge E. Hallyn [off-list ref]
Signed-off-by: James Morris [off-list ref]
Thanks!
quoted hunk ↗ jump to hunk
--- 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
-- Dmitry