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[3.11.y.z,extended,stable] Patch "netlink: Only check file credentials for implicit destinations" has been added to staging queue

Message ID 1403779051-13310-1-git-send-email-luis.henriques@canonical.com
State New
Headers show

Commit Message

Luis Henriques June 26, 2014, 10:37 a.m. UTC 
This is a note to let you know that I have just added a patch titled

    netlink: Only check file credentials for implicit destinations

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

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From fcc559dbd0a53adb22edf5caf0fa550901f380fb Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Fri, 30 May 2014 11:04:00 -0700
Subject: netlink: Only check file credentials for implicit destinations

commit 2d7a85f4b06e9c27ff629f07a524c48074f07f81 upstream.

It was possible to get a setuid root or setcap executable to write to
it's stdout or stderr (which has been set made a netlink socket) and
inadvertently reconfigure the networking stack.

To prevent this we check that both the creator of the socket and
the currentl applications has permission to reconfigure the network
stack.

Unfortunately this breaks Zebra which always uses sendto/sendmsg
and creates it's socket without any privileges.

To keep Zebra working don't bother checking if the creator of the
socket has privilege when a destination address is specified.  Instead
rely exclusively on the privileges of the sender of the socket.

Note from Andy: This is exactly Eric's code except for some comment
clarifications and formatting fixes.  Neither I nor, I think, anyone
else is thrilled with this approach, but I'm hesitant to wait on a
better fix since 3.15 is almost here.

Note to stable maintainers: This is a mess.  An earlier series of
patches in 3.15 fix a rather serious security issue (CVE-2014-0181),
but they did so in a way that breaks Zebra.  The offending series
includes:

    commit aa4cf9452f469f16cea8c96283b641b4576d4a7b
    Author: Eric W. Biederman <ebiederm@xmission.com>
    Date:   Wed Apr 23 14:28:03 2014 -0700

        net: Add variants of capable for use on netlink messages

If a given kernel version is missing that series of fixes, it's
probably worth backporting it and this patch.  if that series is
present, then this fix is critical if you care about Zebra.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 include/linux/netlink.h  | 7 ++++---
 net/netlink/af_netlink.c | 7 ++++++-
 2 files changed, 10 insertions(+), 4 deletions(-)

--
1.9.1
diff mbox

Patch

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 8d11541890ff..8b50a62ef98b 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -16,9 +16,10 @@  static inline struct nlmsghdr *nlmsg_hdr(const struct sk_buff *skb)
 }

 enum netlink_skb_flags {
-	NETLINK_SKB_MMAPED	= 0x1,		/* Packet data is mmaped */
-	NETLINK_SKB_TX		= 0x2,		/* Packet was sent by userspace */
-	NETLINK_SKB_DELIVERED	= 0x4,		/* Packet was delivered */
+	NETLINK_SKB_MMAPED	= 0x1,	/* Packet data is mmaped */
+	NETLINK_SKB_TX		= 0x2,	/* Packet was sent by userspace */
+	NETLINK_SKB_DELIVERED	= 0x4,	/* Packet was delivered */
+	NETLINK_SKB_DST		= 0x8,	/* Dst set in sendto or sendmsg */
 };

 struct netlink_skb_parms {
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 68733f8dd187..7bbc40b63aa4 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1347,7 +1347,9 @@  retry:
 bool __netlink_ns_capable(const struct netlink_skb_parms *nsp,
 			struct user_namespace *user_ns, int cap)
 {
-	return sk_ns_capable(nsp->sk, user_ns, cap);
+	return ((nsp->flags & NETLINK_SKB_DST) ||
+		file_ns_capable(nsp->sk->sk_socket->file, user_ns, cap)) &&
+		ns_capable(user_ns, cap);
 }
 EXPORT_SYMBOL(__netlink_ns_capable);

@@ -2267,6 +2269,7 @@  static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock,
 	struct sk_buff *skb;
 	int err;
 	struct scm_cookie scm;
+	u32 netlink_skb_flags = 0;

 	if (msg->msg_flags&MSG_OOB)
 		return -EOPNOTSUPP;
@@ -2288,6 +2291,7 @@  static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock,
 		if ((dst_group || dst_portid) &&
 		    !netlink_allowed(sock, NL_CFG_F_NONROOT_SEND))
 			goto out;
+		netlink_skb_flags |= NETLINK_SKB_DST;
 	} else {
 		dst_portid = nlk->dst_portid;
 		dst_group = nlk->dst_group;
@@ -2317,6 +2321,7 @@  static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock,
 	NETLINK_CB(skb).portid	= nlk->portid;
 	NETLINK_CB(skb).dst_group = dst_group;
 	NETLINK_CB(skb).creds	= siocb->scm->creds;
+	NETLINK_CB(skb).flags	= netlink_skb_flags;

 	err = -EFAULT;
 	if (memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len)) {