Commit 4ecb9009 authored Jul 25, 2008 by Stephen Hemminger Committed by Linus Torvalds Jul 25, 2008

sysctl: allow override of /proc/sys/net with CAP_NET_ADMIN



Extend the permission check for networking sysctl's to allow modification
when current process has CAP_NET_ADMIN capability and is not root.  This
version uses the until now unused permissions hook to override the mode
value for /proc/sys/net if accessed by a user with capabilities.

Found while working with Quagga.  It is impossible to turn forwarding
on/off through the command interface because Quagga uses secure coding
practice of dropping privledges during initialization and only raising via
capabilities when necessary.  Since the dameon has reset real/effective
uid after initialization, all attempts to access /proc/sys/net variables
will fail.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morgan <morgan@kernel.org>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 99541c23

net/sysctl_net.c

+14 −0

Original line number	Original line	Diff line number	Diff line
	@@ -35,8 +35,22 @@ net_ctl_header_lookup(struct ctl_table_root root, struct nsproxy namespaces)
	return &namespaces->net_ns->sysctl_table_headers;		return &namespaces->net_ns->sysctl_table_headers;
	}		}

			/* Return standard mode bits for table entry. */
			static int net_ctl_permissions(struct ctl_table_root *root,
			struct nsproxy *nsproxy,
			struct ctl_table *table)
			{
			/* Allow network administrator to have same access as root. */
			if (capable(CAP_NET_ADMIN)) {
			int mode = (table->mode >> 6) & 7;
			return (mode << 6) \| (mode << 3) \| mode;
			}
			return table->mode;
			}

	static struct ctl_table_root net_sysctl_root = {		static struct ctl_table_root net_sysctl_root = {
	.lookup = net_ctl_header_lookup,		.lookup = net_ctl_header_lookup,
			.permissions = net_ctl_permissions,
	};		};

	static LIST_HEAD(net_sysctl_ro_tables);		static LIST_HEAD(net_sysctl_ro_tables);