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connector/cn_proc: Allow non-root users access

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There were a couple of reasons for not allowing non-root users access
initially  - one is there was some point no proper receive buffer
management in place for netlink multicast. But that should be long
fixed. See link below for more context.

Second is that some of the messages may contain data that is root only. But
this should be handled with a finer granularity, which is being done at the
protocol layer.  The only problematic protocols are nf_queue and the
firewall netlink. Hence, this restriction for non-root access was relaxed
for NETLINK_ROUTE initially:
https://lore.kernel.org/all/20020612013101.A22399@wotan.suse.de/

This restriction has also been removed for following protocols:
NETLINK_KOBJECT_UEVENT, NETLINK_AUDIT, NETLINK_SOCK_DIAG,
NETLINK_GENERIC, NETLINK_SELINUX.

Since process connector messages are not sensitive (process fork, exit
notifications etc.), and anyone can read /proc data, we can allow non-root
access here. However, since process event notification is not the only
consumer of NETLINK_CONNECTOR, we can make this change even more
fine grained than the protocol level, by checking for multicast group
within the protocol.

Allow non-root access for NETLINK_CONNECTOR via NL_CFG_F_NONROOT_RECV
but add new bind function cn_bind(), which allows non-root access only
for CN_IDX_PROC multicast group.

Signed-off-by: Anjali Kulkarni <anjali.k.kulkarni@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Anjali Kulkarni 2023-07-19 13:18:20 -07:00 committed by David S. Miller
parent 743acf351b
commit bfdfdc2f3b
2 changed files with 19 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/connector/cn_proc.c
View File

@ -410,12 +410,6 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
!task_is_in_init_pid_ns(current))
return;
/* Can only change if privileged. */
if (!__netlink_ns_capable(nsp, &init_user_ns, CAP_NET_ADMIN)) {
err = EPERM;
goto out;
}
if (msg->len == sizeof(*pinput)) {
pinput = (struct proc_input *)msg->data;
mc_op = pinput->mcast_op;

19
drivers/connector/connector.c
View File

@ -166,6 +166,23 @@ static int cn_call_callback(struct sk_buff *skb)
return err;
}
/*
* Allow non-root access for NETLINK_CONNECTOR family having CN_IDX_PROC
* multicast group.
*/
static int cn_bind(struct net *net, int group)
{
unsigned long groups = (unsigned long) group;
if (ns_capable(net->user_ns, CAP_NET_ADMIN))
return 0;
if (test_bit(CN_IDX_PROC - 1, &groups))
return 0;
return -EPERM;
}
static void cn_release(struct sock *sk, unsigned long *groups)
{
if (groups && test_bit(CN_IDX_PROC - 1, groups)) {
@ -261,6 +278,8 @@ static int cn_init(void)
struct netlink_kernel_cfg cfg = {
.groups = CN_NETLINK_USERS + 0xf,
.input = cn_rx_skb,
.flags = NL_CFG_F_NONROOT_RECV,
.bind = cn_bind,
.release = cn_release,
};