[stable 4.4] Security fixes

[Ben Hutchings <ben.hutchings@codethink.co.uk>]

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Greg,

I've found a number of CVEs fixed in upstream a while ago but still
affecting stable branches.  The following commits should fix most of
those for 4.4:

d29216842a85c7970c536108e093963f02714498 (CVE-2016-6213) [backported]
8dfbcc4351a0b6d2f2d77f367552f48ffefafe18 (CVE-2016-7913)
c58d6c93680f28ac58984af61d0a7ebf4319c241 (CVE-2016-7917)
3de81b758853f0b29c61e246679d20b513c4cfec (CVE-2016-8632) [backported]
05692d7005a364add85c6e25a6c4447ce08f913a (CVE-2016-9083, CVE-2016-9084)
9590232bb4f4cc824f3425a6e1349afbe6d6d2b7 (CVE-2016-9120)
43a6684519ab0a6c52024b5e25322476cabad893 (CVE-2017-2671)
321027c1fe77f892f4ea07846aeae08cefbbb290 (CVE-2017-6001) [backported]
8f8d28e4d6d815a391285e121c3a53a0b6cb9e7b (CVE-2017-7308)
bcc5364bdcfe131e6379363f089e7b4108d35b70 (CVE-2017-7308)

I've attached patches for those that needed work to backport.

CVE-2017-7308 isn't yet fixed in 4.9 or 4.10, but David Miller has the
patches queued up.

I should be able to provide you with a (much longer) list for 3.18
later.

Ben.

-- 
Ben Hutchings
Software Developer, Codethink Ltd.


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From ca2e63098cf9189b277bf57ca3f1b2f9d03fac4b Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Wed, 28 Sep 2016 00:27:17 -0500
Subject: [PATCH 1/3] mnt: Add a per mount namespace limit on the number of
 mounts

commit d29216842a85c7970c536108e093963f02714498 upstream.

CAI Qian <caiqian@redhat.com> pointed out that the semantics
of shared subtrees make it possible to create an exponentially
increasing number of mounts in a mount namespace.

    mkdir /tmp/1 /tmp/2
    mount --make-rshared /
    for i in $(seq 1 20) ; do mount --bind /tmp/1 /tmp/2 ; done

Will create create 2^20 or 1048576 mounts, which is a practical problem
as some people have managed to hit this by accident.

As such CVE-2016-6213 was assigned.

Ian Kent <raven@themaw.net> described the situation for autofs users
as follows:

> The number of mounts for direct mount maps is usually not very large because of
> the way they are implemented, large direct mount maps can have performance
> problems. There can be anywhere from a few (likely case a few hundred) to less
> than 10000, plus mounts that have been triggered and not yet expired.
>
> Indirect mounts have one autofs mount at the root plus the number of mounts that
> have been triggered and not yet expired.
>
> The number of autofs indirect map entries can range from a few to the common
> case of several thousand and in rare cases up to between 30000 and 50000. I've
> not heard of people with maps larger than 50000 entries.
>
> The larger the number of map entries the greater the possibility for a large
> number of active mounts so it's not hard to expect cases of a 1000 or somewhat
> more active mounts.

So I am setting the default number of mounts allowed per mount
namespace at 100,000.  This is more than enough for any use case I
know of, but small enough to quickly stop an exponential increase
in mounts.  Which should be perfect to catch misconfigurations and
malfunctioning programs.

For anyone who needs a higher limit this can be changed by writing
to the new /proc/sys/fs/mount-max sysctl.

Tested-by: CAI Qian <caiqian@redhat.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
[bwh: Backported to 4.4: adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
---
 Documentation/sysctl/fs.txt |  7 +++++++
 fs/mount.h                  |  2 ++
 fs/namespace.c              | 50 ++++++++++++++++++++++++++++++++++++++++++++-
 fs/pnode.c                  |  2 +-
 fs/pnode.h                  |  1 +
 include/linux/mount.h       |  2 ++
 kernel/sysctl.c             |  9 ++++++++
 7 files changed, 71 insertions(+), 2 deletions(-)

diff --git a/Documentation/sysctl/fs.txt b/Documentation/sysctl/fs.txt
index 302b5ed616a6..35e17f748ca7 100644
--- a/Documentation/sysctl/fs.txt
+++ b/Documentation/sysctl/fs.txt
@@ -265,6 +265,13 @@ aio-nr can grow to.
 
 ==============================================================
 
+mount-max:
+
+This denotes the maximum number of mounts that may exist
+in a mount namespace.
+
+==============================================================
+
 
 2. /proc/sys/fs/binfmt_misc
 ----------------------------------------------------------
diff --git a/fs/mount.h b/fs/mount.h
index 3dc7dea5a357..13a4ebbbaa74 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -13,6 +13,8 @@ struct mnt_namespace {
 	u64			seq;	/* Sequence number to prevent loops */
 	wait_queue_head_t poll;
 	u64 event;
+	unsigned int		mounts; /* # of mounts in the namespace */
+	unsigned int		pending_mounts;
 };
 
 struct mnt_pcp {
diff --git a/fs/namespace.c b/fs/namespace.c
index 7df3d406d3e0..f26d18d69712 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -27,6 +27,9 @@
 #include "pnode.h"
 #include "internal.h"
 
+/* Maximum number of mounts in a mount namespace */
+unsigned int sysctl_mount_max __read_mostly = 100000;
+
 static unsigned int m_hash_mask __read_mostly;
 static unsigned int m_hash_shift __read_mostly;
 static unsigned int mp_hash_mask __read_mostly;
@@ -925,6 +928,9 @@ static void commit_tree(struct mount *mnt)
 
 	list_splice(&head, n->list.prev);
 
+	n->mounts += n->pending_mounts;
+	n->pending_mounts = 0;
+
 	__attach_mnt(mnt, parent);
 	touch_mnt_namespace(n);
 }
@@ -1445,11 +1451,16 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
 		propagate_umount(&tmp_list);
 
 	while (!list_empty(&tmp_list)) {
+		struct mnt_namespace *ns;
 		bool disconnect;
 		p = list_first_entry(&tmp_list, struct mount, mnt_list);
 		list_del_init(&p->mnt_expire);
 		list_del_init(&p->mnt_list);
-		__touch_mnt_namespace(p->mnt_ns);
+		ns = p->mnt_ns;
+		if (ns) {
+			ns->mounts--;
+			__touch_mnt_namespace(ns);
+		}
 		p->mnt_ns = NULL;
 		if (how & UMOUNT_SYNC)
 			p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
@@ -1850,6 +1861,28 @@ static int invent_group_ids(struct mount *mnt, bool recurse)
 	return 0;
 }
 
+int count_mounts(struct mnt_namespace *ns, struct mount *mnt)
+{
+	unsigned int max = READ_ONCE(sysctl_mount_max);
+	unsigned int mounts = 0, old, pending, sum;
+	struct mount *p;
+
+	for (p = mnt; p; p = next_mnt(p, mnt))
+		mounts++;
+
+	old = ns->mounts;
+	pending = ns->pending_mounts;
+	sum = old + pending;
+	if ((old > sum) ||
+	    (pending > sum) ||
+	    (max < sum) ||
+	    (mounts > (max - sum)))
+		return -ENOSPC;
+
+	ns->pending_mounts = pending + mounts;
+	return 0;
+}
+
 /*
  *  @source_mnt : mount tree to be attached
  *  @nd         : place the mount tree @source_mnt is attached
@@ -1919,6 +1952,7 @@ static int attach_recursive_mnt(struct mount *source_mnt,
 			struct path *parent_path)
 {
 	HLIST_HEAD(tree_list);
+	struct mnt_namespace *ns = dest_mnt->mnt_ns;
 	struct mountpoint *smp;
 	struct mount *child, *p;
 	struct hlist_node *n;
@@ -1931,6 +1965,13 @@ static int attach_recursive_mnt(struct mount *source_mnt,
 	if (IS_ERR(smp))
 		return PTR_ERR(smp);
 
+	/* Is there space to add these mounts to the mount namespace? */
+	if (!parent_path) {
+		err = count_mounts(ns, source_mnt);
+		if (err)
+			goto out;
+	}
+
 	if (IS_MNT_SHARED(dest_mnt)) {
 		err = invent_group_ids(source_mnt, true);
 		if (err)
@@ -1970,11 +2011,14 @@ static int attach_recursive_mnt(struct mount *source_mnt,
  out_cleanup_ids:
 	while (!hlist_empty(&tree_list)) {
 		child = hlist_entry(tree_list.first, struct mount, mnt_hash);
+		child->mnt_parent->mnt_ns->pending_mounts = 0;
 		umount_tree(child, UMOUNT_SYNC);
 	}
 	unlock_mount_hash();
 	cleanup_group_ids(source_mnt, NULL);
  out:
+	ns->pending_mounts = 0;
+
 	read_seqlock_excl(&mount_lock);
 	put_mountpoint(smp);
 	read_sequnlock_excl(&mount_lock);
@@ -2804,6 +2848,8 @@ static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
 	init_waitqueue_head(&new_ns->poll);
 	new_ns->event = 0;
 	new_ns->user_ns = get_user_ns(user_ns);
+	new_ns->mounts = 0;
+	new_ns->pending_mounts = 0;
 	return new_ns;
 }
 
@@ -2853,6 +2899,7 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
 	q = new;
 	while (p) {
 		q->mnt_ns = new_ns;
+		new_ns->mounts++;
 		if (new_fs) {
 			if (&p->mnt == new_fs->root.mnt) {
 				new_fs->root.mnt = mntget(&q->mnt);
@@ -2891,6 +2938,7 @@ static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
 		struct mount *mnt = real_mount(m);
 		mnt->mnt_ns = new_ns;
 		new_ns->root = mnt;
+		new_ns->mounts++;
 		list_add(&mnt->mnt_list, &new_ns->list);
 	} else {
 		mntput(m);
diff --git a/fs/pnode.c b/fs/pnode.c
index b9f2af59b9a6..b394ca5307ec 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -259,7 +259,7 @@ static int propagate_one(struct mount *m)
 		read_sequnlock_excl(&mount_lock);
 	}
 	hlist_add_head(&child->mnt_hash, list);
-	return 0;
+	return count_mounts(m->mnt_ns, child);
 }
 
 /*
diff --git a/fs/pnode.h b/fs/pnode.h
index 623f01772bec..dc87e65becd2 100644
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -54,4 +54,5 @@ void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp,
 struct mount *copy_tree(struct mount *, struct dentry *, int);
 bool is_path_reachable(struct mount *, struct dentry *,
 			 const struct path *root);
+int count_mounts(struct mnt_namespace *ns, struct mount *mnt);
 #endif /* _LINUX_PNODE_H */
diff --git a/include/linux/mount.h b/include/linux/mount.h
index f822c3c11377..dc6cd800cd5d 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -95,4 +95,6 @@ extern void mark_mounts_for_expiry(struct list_head *mounts);
 
 extern dev_t name_to_dev_t(const char *name);
 
+extern unsigned int sysctl_mount_max;
+
 #endif /* _LINUX_MOUNT_H */
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 2f0d157258a2..300d64162aff 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -65,6 +65,7 @@
 #include <linux/sched/sysctl.h>
 #include <linux/kexec.h>
 #include <linux/bpf.h>
+#include <linux/mount.h>
 
 #include <asm/uaccess.h>
 #include <asm/processor.h>
@@ -1749,6 +1750,14 @@ static struct ctl_table fs_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_doulongvec_minmax,
 	},
+	{
+		.procname	= "mount-max",
+		.data		= &sysctl_mount_max,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &one,
+	},
 	{ }
 };
 
-- 
2.11.0


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From 7975af4c56dcc79851602f3154c06642c89f5ce3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michal=20Kube=C4=8Dek?= <mkubecek@suse.cz>
Date: Fri, 2 Dec 2016 09:33:41 +0100
Subject: [PATCH 2/3] tipc: check minimum bearer MTU
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit 3de81b758853f0b29c61e246679d20b513c4cfec upstream.

Qian Zhang (张谦) reported a potential socket buffer overflow in
tipc_msg_build() which is also known as CVE-2016-8632: due to
insufficient checks, a buffer overflow can occur if MTU is too short for
even tipc headers. As anyone can set device MTU in a user/net namespace,
this issue can be abused by a regular user.

As agreed in the discussion on Ben Hutchings' original patch, we should
check the MTU at the moment a bearer is attached rather than for each
processed packet. We also need to repeat the check when bearer MTU is
adjusted to new device MTU. UDP case also needs a check to avoid
overflow when calculating bearer MTU.

Fixes: b97bf3fd8f6a ("[TIPC] Initial merge")
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Reported-by: Qian Zhang (张谦) <zhangqian-c@360.cn>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 4.4:
 - Adjust context
 - NETDEV_GOING_DOWN and NETDEV_CHANGEMTU cases in net notifier were combined]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
---
 net/tipc/bearer.c    | 13 +++++++++++--
 net/tipc/bearer.h    | 13 +++++++++++++
 net/tipc/udp_media.c |  5 +++++
 3 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
index 648f2a67f314..cb1381513c82 100644
--- a/net/tipc/bearer.c
+++ b/net/tipc/bearer.c
@@ -381,6 +381,10 @@ int tipc_enable_l2_media(struct net *net, struct tipc_bearer *b,
 	dev = dev_get_by_name(net, driver_name);
 	if (!dev)
 		return -ENODEV;
+	if (tipc_mtu_bad(dev, 0)) {
+		dev_put(dev);
+		return -EINVAL;
+	}
 
 	/* Associate TIPC bearer with L2 bearer */
 	rcu_assign_pointer(b->media_ptr, dev);
@@ -570,14 +574,19 @@ static int tipc_l2_device_event(struct notifier_block *nb, unsigned long evt,
 	if (!b_ptr)
 		return NOTIFY_DONE;
 
-	b_ptr->mtu = dev->mtu;
-
 	switch (evt) {
 	case NETDEV_CHANGE:
 		if (netif_carrier_ok(dev))
 			break;
 	case NETDEV_GOING_DOWN:
+		tipc_reset_bearer(net, b_ptr);
+		break;
 	case NETDEV_CHANGEMTU:
+		if (tipc_mtu_bad(dev, 0)) {
+			bearer_disable(net, b_ptr);
+			break;
+		}
+		b_ptr->mtu = dev->mtu;
 		tipc_reset_bearer(net, b_ptr);
 		break;
 	case NETDEV_CHANGEADDR:
diff --git a/net/tipc/bearer.h b/net/tipc/bearer.h
index 552185bc4773..5f11e18b1fa1 100644
--- a/net/tipc/bearer.h
+++ b/net/tipc/bearer.h
@@ -39,6 +39,7 @@
 
 #include "netlink.h"
 #include "core.h"
+#include "msg.h"
 #include <net/genetlink.h>
 
 #define MAX_MEDIA	3
@@ -61,6 +62,9 @@
 #define TIPC_MEDIA_TYPE_IB	2
 #define TIPC_MEDIA_TYPE_UDP	3
 
+/* minimum bearer MTU */
+#define TIPC_MIN_BEARER_MTU	(MAX_H_SIZE + INT_H_SIZE)
+
 /**
  * struct tipc_node_map - set of node identifiers
  * @count: # of nodes in set
@@ -226,4 +230,13 @@ void tipc_bearer_xmit(struct net *net, u32 bearer_id,
 void tipc_bearer_bc_xmit(struct net *net, u32 bearer_id,
 			 struct sk_buff_head *xmitq);
 
+/* check if device MTU is too low for tipc headers */
+static inline bool tipc_mtu_bad(struct net_device *dev, unsigned int reserve)
+{
+	if (dev->mtu >= TIPC_MIN_BEARER_MTU + reserve)
+		return false;
+	netdev_warn(dev, "MTU too low for tipc bearer\n");
+	return true;
+}
+
 #endif	/* _TIPC_BEARER_H */
diff --git a/net/tipc/udp_media.c b/net/tipc/udp_media.c
index 6af78c6276b4..39497a40b96b 100644
--- a/net/tipc/udp_media.c
+++ b/net/tipc/udp_media.c
@@ -376,6 +376,11 @@ static int tipc_udp_enable(struct net *net, struct tipc_bearer *b,
 		udp_conf.local_ip.s_addr = htonl(INADDR_ANY);
 		udp_conf.use_udp_checksums = false;
 		ub->ifindex = dev->ifindex;
+		if (tipc_mtu_bad(dev, sizeof(struct iphdr) +
+				      sizeof(struct udphdr))) {
+			err = -EINVAL;
+			goto err;
+		}
 		b->mtu = dev->mtu - sizeof(struct iphdr)
 			- sizeof(struct udphdr);
 #if IS_ENABLED(CONFIG_IPV6)
-- 
2.11.0


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From 325e7202d8d71aeb48034bf4f692d57146c95370 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Wed, 11 Jan 2017 21:09:50 +0100
Subject: [PATCH 3/3] perf/core: Fix concurrent sys_perf_event_open() vs.
 'move_group' race

commit 321027c1fe77f892f4ea07846aeae08cefbbb290 upstream.

Di Shen reported a race between two concurrent sys_perf_event_open()
calls where both try and move the same pre-existing software group
into a hardware context.

The problem is exactly that described in commit:

  f63a8daa5812 ("perf: Fix event->ctx locking")

... where, while we wait for a ctx->mutex acquisition, the event->ctx
relation can have changed under us.

That very same commit failed to recognise sys_perf_event_context() as an
external access vector to the events and thereby didn't apply the
established locking rules correctly.

So while one sys_perf_event_open() call is stuck waiting on
mutex_lock_double(), the other (which owns said locks) moves the group
about. So by the time the former sys_perf_event_open() acquires the
locks, the context we've acquired is stale (and possibly dead).

Apply the established locking rules as per perf_event_ctx_lock_nested()
to the mutex_lock_double() for the 'move_group' case. This obviously means
we need to validate state after we acquire the locks.

Reported-by: Di Shen (Keen Lab)
Tested-by: John Dias <joaodias@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Min Chong <mchong@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Fixes: f63a8daa5812 ("perf: Fix event->ctx locking")
Link: http://lkml.kernel.org/r/20170106131444.GZ3174@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[bwh: Backported to 4.4:
 - Test perf_event::group_flags instead of group_caps
 - Adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
---
 kernel/events/core.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 53 insertions(+), 4 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index e4b5494f05f8..784ab8fe8714 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8250,6 +8250,37 @@ static int perf_event_set_clock(struct perf_event *event, clockid_t clk_id)
 	return 0;
 }
 
+/*
+ * Variation on perf_event_ctx_lock_nested(), except we take two context
+ * mutexes.
+ */
+static struct perf_event_context *
+__perf_event_ctx_lock_double(struct perf_event *group_leader,
+			     struct perf_event_context *ctx)
+{
+	struct perf_event_context *gctx;
+
+again:
+	rcu_read_lock();
+	gctx = READ_ONCE(group_leader->ctx);
+	if (!atomic_inc_not_zero(&gctx->refcount)) {
+		rcu_read_unlock();
+		goto again;
+	}
+	rcu_read_unlock();
+
+	mutex_lock_double(&gctx->mutex, &ctx->mutex);
+
+	if (group_leader->ctx != gctx) {
+		mutex_unlock(&ctx->mutex);
+		mutex_unlock(&gctx->mutex);
+		put_ctx(gctx);
+		goto again;
+	}
+
+	return gctx;
+}
+
 /**
  * sys_perf_event_open - open a performance event, associate it to a task/cpu
  *
@@ -8486,8 +8517,26 @@ SYSCALL_DEFINE5(perf_event_open,
 	}
 
 	if (move_group) {
-		gctx = group_leader->ctx;
-		mutex_lock_double(&gctx->mutex, &ctx->mutex);
+		gctx = __perf_event_ctx_lock_double(group_leader, ctx);
+
+		/*
+		 * Check if we raced against another sys_perf_event_open() call
+		 * moving the software group underneath us.
+		 */
+		if (!(group_leader->group_flags & PERF_GROUP_SOFTWARE)) {
+			/*
+			 * If someone moved the group out from under us, check
+			 * if this new event wound up on the same ctx, if so
+			 * its the regular !move_group case, otherwise fail.
+			 */
+			if (gctx != ctx) {
+				err = -EINVAL;
+				goto err_locked;
+			} else {
+				perf_event_ctx_unlock(group_leader, gctx);
+				move_group = 0;
+			}
+		}
 	} else {
 		mutex_lock(&ctx->mutex);
 	}
@@ -8582,7 +8631,7 @@ SYSCALL_DEFINE5(perf_event_open,
 	perf_unpin_context(ctx);
 
 	if (move_group)
-		mutex_unlock(&gctx->mutex);
+		perf_event_ctx_unlock(group_leader, gctx);
 	mutex_unlock(&ctx->mutex);
 
 	if (task) {
@@ -8610,7 +8659,7 @@ SYSCALL_DEFINE5(perf_event_open,
 
 err_locked:
 	if (move_group)
-		mutex_unlock(&gctx->mutex);
+		perf_event_ctx_unlock(group_leader, gctx);
 	mutex_unlock(&ctx->mutex);
 /* err_file: */
 	fput(event_file);
-- 
2.11.0