mnt: Add a per mount namespace limit on the number of mounts (CVE-2016-6213)
This commit is contained in:
parent
b67bd212fa
commit
ceb75c4337
|
@ -236,6 +236,8 @@ linux (4.8.11-1) UNRELEASED; urgency=medium
|
||||||
* mpi: Fix NULL ptr dereference in mpi_powm() (CVE-2016-8650)
|
* mpi: Fix NULL ptr dereference in mpi_powm() (CVE-2016-8650)
|
||||||
* vfio/pci: Fix integer overflows, bitmask check (CVE-2016-9083
|
* vfio/pci: Fix integer overflows, bitmask check (CVE-2016-9083
|
||||||
CVE-2016-9084)
|
CVE-2016-9084)
|
||||||
|
* mnt: Add a per mount namespace limit on the number of mounts
|
||||||
|
(CVE-2016-6213)
|
||||||
|
|
||||||
[ Ben Hutchings ]
|
[ Ben Hutchings ]
|
||||||
* [arm64] Enable more drivers for X-Gene (Really closes: #840061):
|
* [arm64] Enable more drivers for X-Gene (Really closes: #840061):
|
||||||
|
|
266
debian/patches/bugfix/all/mnt-Add-a-per-mount-namespace-limit-on-the-number-of.patch
vendored
Normal file
266
debian/patches/bugfix/all/mnt-Add-a-per-mount-namespace-limit-on-the-number-of.patch
vendored
Normal file
|
@ -0,0 +1,266 @@
|
||||||
|
From: "Eric W. Biederman" <ebiederm@xmission.com>
|
||||||
|
Date: Wed, 28 Sep 2016 00:27:17 -0500
|
||||||
|
Subject: mnt: Add a per mount namespace limit on the number of mounts
|
||||||
|
Origin: https://git.kernel.org/linus/d29216842a85c7970c536108e093963f02714498
|
||||||
|
|
||||||
|
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>
|
||||||
|
[carnil: Adjust context for 4.8]
|
||||||
|
---
|
||||||
|
Documentation/sysctl/fs.txt | 7 +++++++
|
||||||
|
fs/mount.h | 2 ++
|
||||||
|
fs/namespace.c | 49 ++++++++++++++++++++++++++++++++++++++++++++-
|
||||||
|
fs/pnode.c | 2 +-
|
||||||
|
fs/pnode.h | 1 +
|
||||||
|
include/linux/mount.h | 2 ++
|
||||||
|
kernel/sysctl.c | 9 +++++++++
|
||||||
|
7 files changed, 70 insertions(+), 2 deletions(-)
|
||||||
|
|
||||||
|
--- 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
|
||||||
|
----------------------------------------------------------
|
||||||
|
--- 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 {
|
||||||
|
--- 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;
|
||||||
|
@@ -900,6 +903,9 @@ static void commit_tree(struct mount *mn
|
||||||
|
|
||||||
|
list_splice(&head, n->list.prev);
|
||||||
|
|
||||||
|
+ n->mounts += n->pending_mounts;
|
||||||
|
+ n->pending_mounts = 0;
|
||||||
|
+
|
||||||
|
attach_shadowed(mnt, parent, shadows);
|
||||||
|
touch_mnt_namespace(n);
|
||||||
|
}
|
||||||
|
@@ -1420,11 +1426,16 @@ static void umount_tree(struct mount *mn
|
||||||
|
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;
|
||||||
|
@@ -1842,6 +1853,28 @@ static int invent_group_ids(struct mount
|
||||||
|
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
|
||||||
|
@@ -1911,10 +1944,18 @@ static int attach_recursive_mnt(struct m
|
||||||
|
struct path *parent_path)
|
||||||
|
{
|
||||||
|
HLIST_HEAD(tree_list);
|
||||||
|
+ struct mnt_namespace *ns = dest_mnt->mnt_ns;
|
||||||
|
struct mount *child, *p;
|
||||||
|
struct hlist_node *n;
|
||||||
|
int err;
|
||||||
|
|
||||||
|
+ /* 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)
|
||||||
|
@@ -1951,11 +1992,13 @@ static int attach_recursive_mnt(struct m
|
||||||
|
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;
|
||||||
|
return err;
|
||||||
|
}
|
||||||
|
|
||||||
|
@@ -2758,6 +2801,8 @@ static struct mnt_namespace *alloc_mnt_n
|
||||||
|
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;
|
||||||
|
}
|
||||||
|
|
||||||
|
@@ -2807,6 +2852,7 @@ struct mnt_namespace *copy_mnt_ns(unsign
|
||||||
|
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);
|
||||||
|
@@ -2845,6 +2891,7 @@ static struct mnt_namespace *create_mnt_
|
||||||
|
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);
|
||||||
|
--- 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);
|
||||||
|
}
|
||||||
|
|
||||||
|
/*
|
||||||
|
--- a/fs/pnode.h
|
||||||
|
+++ b/fs/pnode.h
|
||||||
|
@@ -52,4 +52,5 @@ void mnt_set_mountpoint(struct mount *,
|
||||||
|
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 */
|
||||||
|
--- a/include/linux/mount.h
|
||||||
|
+++ b/include/linux/mount.h
|
||||||
|
@@ -96,4 +96,6 @@ extern void mark_mounts_for_expiry(struc
|
||||||
|
|
||||||
|
extern dev_t name_to_dev_t(const char *name);
|
||||||
|
|
||||||
|
+extern unsigned int sysctl_mount_max;
|
||||||
|
+
|
||||||
|
#endif /* _LINUX_MOUNT_H */
|
||||||
|
--- 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>
|
||||||
|
@@ -1850,6 +1851,14 @@ 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,
|
||||||
|
+ },
|
||||||
|
{ }
|
||||||
|
};
|
||||||
|
|
|
@ -100,6 +100,7 @@ bugfix/all/fs-Give-dentry-to-inode_change_ok-instead-of-inode.patch
|
||||||
bugfix/all/fs-Avoid-premature-clearing-of-capabilities.patch
|
bugfix/all/fs-Avoid-premature-clearing-of-capabilities.patch
|
||||||
bugfix/all/mpi-Fix-NULL-ptr-dereference-in-mpi_powm-ver-3.patch
|
bugfix/all/mpi-Fix-NULL-ptr-dereference-in-mpi_powm-ver-3.patch
|
||||||
bugfix/all/vfio-pci-Fix-integer-overflows-bitmask-check.patch
|
bugfix/all/vfio-pci-Fix-integer-overflows-bitmask-check.patch
|
||||||
|
bugfix/all/mnt-Add-a-per-mount-namespace-limit-on-the-number-of.patch
|
||||||
|
|
||||||
# ABI maintenance
|
# ABI maintenance
|
||||||
|
|
||||||
|
|
Loading…
Reference in New Issue