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88ba09df23
On Tue, 20 Aug 2013 11:40:04 -0500 Eric Sandeen <sandeen@redhat.com> wrote:
> This was brought up in a Red Hat bug (which may be marked private, I'm sorry):
>
> Bug 987055 - open O_WRONLY succeeds on some root owned files in /proc for process running with unprivileged EUID
>
> "On RHEL7 some of the files in /proc can be opened for writing by an unprivileged EUID."
>
> The flaw existed upstream as well last I checked.
>
> This commit in kernel v3.8 caused the regression:
>
> commit cff109768b
> Author: Eric W. Biederman <ebiederm@xmission.com>
> Date: Fri Nov 16 03:03:01 2012 +0000
>
> net: Update the per network namespace sysctls to be available to the network namespace owner
>
> - Allow anyone with CAP_NET_ADMIN rights in the user namespace of the
> the netowrk namespace to change sysctls.
> - Allow anyone the uid of the user namespace root the same
> permissions over the network namespace sysctls as the global root.
> - Allow anyone with gid of the user namespace root group the same
> permissions over the network namespace sysctl as the global root group.
>
> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
> Signed-off-by: David S. Miller <davem@davemloft.net>
>
> because it changed /sys/net's special permission handler to test current_uid, not
> current_euid; same for current_gid/current_egid.
>
> So in this case, root cannot drop privs via set[ug]id, and retains all privs
> in this codepath.
Modify the code to use current_euid(), and in_egroup_p, as in done
in fs/proc/proc_sysctl.c:test_perm()
Cc: stable@vger.kernel.org
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Reported-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
115 lines
2.8 KiB
C
115 lines
2.8 KiB
C
/* -*- linux-c -*-
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* sysctl_net.c: sysctl interface to net subsystem.
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*
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* Begun April 1, 1996, Mike Shaver.
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* Added /proc/sys/net directories for each protocol family. [MS]
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*
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* Revision 1.2 1996/05/08 20:24:40 shaver
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* Added bits for NET_BRIDGE and the NET_IPV4_ARP stuff and
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* NET_IPV4_IP_FORWARD.
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*
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*
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*/
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#include <linux/mm.h>
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#include <linux/export.h>
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#include <linux/sysctl.h>
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#include <linux/nsproxy.h>
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#include <net/sock.h>
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#ifdef CONFIG_INET
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#include <net/ip.h>
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#endif
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#ifdef CONFIG_NET
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#include <linux/if_ether.h>
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#endif
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static struct ctl_table_set *
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net_ctl_header_lookup(struct ctl_table_root *root, struct nsproxy *namespaces)
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{
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return &namespaces->net_ns->sysctls;
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}
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static int is_seen(struct ctl_table_set *set)
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{
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return ¤t->nsproxy->net_ns->sysctls == set;
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}
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/* Return standard mode bits for table entry. */
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static int net_ctl_permissions(struct ctl_table_header *head,
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struct ctl_table *table)
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{
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struct net *net = container_of(head->set, struct net, sysctls);
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kuid_t root_uid = make_kuid(net->user_ns, 0);
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kgid_t root_gid = make_kgid(net->user_ns, 0);
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/* Allow network administrator to have same access as root. */
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if (ns_capable(net->user_ns, CAP_NET_ADMIN) ||
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uid_eq(root_uid, current_euid())) {
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int mode = (table->mode >> 6) & 7;
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return (mode << 6) | (mode << 3) | mode;
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}
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/* Allow netns root group to have the same access as the root group */
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if (in_egroup_p(root_gid)) {
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int mode = (table->mode >> 3) & 7;
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return (mode << 3) | mode;
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}
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return table->mode;
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}
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static struct ctl_table_root net_sysctl_root = {
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.lookup = net_ctl_header_lookup,
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.permissions = net_ctl_permissions,
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};
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static int __net_init sysctl_net_init(struct net *net)
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{
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setup_sysctl_set(&net->sysctls, &net_sysctl_root, is_seen);
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return 0;
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}
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static void __net_exit sysctl_net_exit(struct net *net)
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{
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retire_sysctl_set(&net->sysctls);
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}
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static struct pernet_operations sysctl_pernet_ops = {
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.init = sysctl_net_init,
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.exit = sysctl_net_exit,
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};
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static struct ctl_table_header *net_header;
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__init int net_sysctl_init(void)
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{
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static struct ctl_table empty[1];
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int ret = -ENOMEM;
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/* Avoid limitations in the sysctl implementation by
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* registering "/proc/sys/net" as an empty directory not in a
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* network namespace.
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*/
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net_header = register_sysctl("net", empty);
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if (!net_header)
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goto out;
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ret = register_pernet_subsys(&sysctl_pernet_ops);
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if (ret)
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goto out;
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register_sysctl_root(&net_sysctl_root);
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out:
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return ret;
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}
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struct ctl_table_header *register_net_sysctl(struct net *net,
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const char *path, struct ctl_table *table)
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{
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return __register_sysctl_table(&net->sysctls, path, table);
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}
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EXPORT_SYMBOL_GPL(register_net_sysctl);
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void unregister_net_sysctl_table(struct ctl_table_header *header)
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{
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unregister_sysctl_table(header);
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}
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EXPORT_SYMBOL_GPL(unregister_net_sysctl_table);
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