This is a note to let you know that I've just added the patch titled
netlink: Only check file credentials for implicit
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
netlink-only-check-file-credentials-for-implicit.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Thu Jun 19 10:28:46 PDT 2014
From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Date: Fri, 30 May 2014 11:04:00 -0700
Subject: netlink: Only check file credentials for implicit
destinations
From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
[ Upstream commit 2d7a85f4b06e9c27ff629f07a524c48074f07f81 ]
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@xxxxxxxxxxxx>
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.
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/netlink.h | 7 ++++---
net/netlink/af_netlink.c | 7 ++++++-
2 files changed, 10 insertions(+), 4 deletions(-)
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -16,9 +16,10 @@ static inline struct nlmsghdr *nlmsg_hdr
}
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 {
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1373,7 +1373,9 @@ 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);
@@ -2293,6 +2295,7 @@ static int netlink_sendmsg(struct kiocb
struct sk_buff *skb;
int err;
struct scm_cookie scm;
+ u32 netlink_skb_flags = 0;
if (msg->msg_flags&MSG_OOB)
return -EOPNOTSUPP;
@@ -2314,6 +2317,7 @@ static int netlink_sendmsg(struct kiocb
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;
@@ -2343,6 +2347,7 @@ static int netlink_sendmsg(struct kiocb
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)) {
Patches currently in stable-queue which might be from ebiederm@xxxxxxxxxxxx are
queue-3.14/net-add-variants-of-capable-for-use-on-on-sockets.patch
queue-3.14/net-use-netlink_ns_capable-to-verify-the-permisions.patch
queue-3.14/net-move-the-permission-check-in.patch
queue-3.14/ima-introduce-ima_kernel_read.patch
queue-3.14/net-add-variants-of-capable-for-use-on-netlink.patch
queue-3.14/netlink-rename-netlink_capable-netlink_allowed.patch
queue-3.14/netlink-only-check-file-credentials-for-implicit.patch
--
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