--- /dev/null
+From 5506202b83e65b844309093e712b5b507eb1e403 Mon Sep 17 00:00:00 2001
+From: Jann Horn <jannh@google.com>
+Date: Tue, 13 Nov 2018 07:42:38 +0000
+Subject: [PATCH 09/11] userns: also map extents in the reverse map to kernel
+ IDs
+
+BugLink: https://launchpad.net/bugs/1801924
+
+The current logic first clones the extent array and sorts both copies, then
+maps the lower IDs of the forward mapping into the lower namespace, but
+doesn't map the lower IDs of the reverse mapping.
+
+This means that code in a nested user namespace with >5 extents will see
+incorrect IDs. It also breaks some access checks, like
+inode_owner_or_capable() and privileged_wrt_inode_uidgid(), so a process
+can incorrectly appear to be capable relative to an inode.
+
+To fix it, we have to make sure that the "lower_first" members of extents
+in both arrays are translated; and we have to make sure that the reverse
+map is sorted *after* the translation (since otherwise the translation can
+break the sorting).
+
+This is CVE-2018-18955.
+
+Fixes: 6397fac4915a ("userns: bump idmap limits to 340")
+Cc: stable@vger.kernel.org
+Signed-off-by: Jann Horn <jannh@google.com>
+Tested-by: Eric W. Biederman <ebiederm@xmission.com>
+Reviewed-by: Eric W. Biederman <ebiederm@xmission.com>
+Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
+
+CVE-2018-18955
+
+(cherry picked from commit d2f007dbe7e4c9583eea6eb04d60001e85c6f1bd)
+Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
+Acked-by: Colin King <colin.king@canonical.com>
+Acked-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
+Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
+---
+ kernel/user_namespace.c | 12 ++++++++----
+ 1 file changed, 8 insertions(+), 4 deletions(-)
+
+diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
+index 08d638386b83..12de8c144db9 100644
+--- a/kernel/user_namespace.c
++++ b/kernel/user_namespace.c
+@@ -983,10 +983,6 @@ static ssize_t map_write(struct file *file, const char __user *buf,
+ if (!new_idmap_permitted(file, ns, cap_setid, &new_map))
+ goto out;
+
+- ret = sort_idmaps(&new_map);
+- if (ret < 0)
+- goto out;
+-
+ ret = -EPERM;
+ /* Map the lower ids from the parent user namespace to the
+ * kernel global id space.
+@@ -1013,6 +1009,14 @@ static ssize_t map_write(struct file *file, const char __user *buf,
+ e->lower_first = lower_first;
+ }
+
++ /*
++ * If we want to use binary search for lookup, this clones the extent
++ * array and sorts both copies.
++ */
++ ret = sort_idmaps(&new_map);
++ if (ret < 0)
++ goto out;
++
+ /* Install the map */
+ if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) {
+ memcpy(map->extent, new_map.extent,
+--
+2.11.0
+
--- /dev/null
+From 3918a0379c7d37ce5d348ec6c2439d744a92a1f8 Mon Sep 17 00:00:00 2001
+From: "Eric W. Biederman" <ebiederm@xmission.com>
+Date: Tue, 13 Nov 2018 07:44:37 +0000
+Subject: [PATCH 10/11] mount: Retest MNT_LOCKED in do_umount
+
+BugLink: https://launchpad.net/bugs/1789161
+
+It was recently pointed out that the one instance of testing MNT_LOCKED
+outside of the namespace_sem is in ksys_umount.
+
+Fix that by adding a test inside of do_umount with namespace_sem and
+the mount_lock held. As it helps to fail fails the existing test is
+maintained with an additional comment pointing out that it may be racy
+because the locks are not held.
+
+Cc: stable@vger.kernel.org
+Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
+Fixes: 5ff9d8a65ce8 ("vfs: Lock in place mounts from more privileged users")
+Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
+(cherry picked from commit 25d202ed820ee347edec0bf3bf553544556bf64b)
+Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
+Acked-by: Colin King <colin.king@canonical.com>
+Acked-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
+Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
+---
+ fs/namespace.c | 10 ++++++++--
+ 1 file changed, 8 insertions(+), 2 deletions(-)
+
+diff --git a/fs/namespace.c b/fs/namespace.c
+index 570c9672ac9f..dcf107925150 100644
+--- a/fs/namespace.c
++++ b/fs/namespace.c
+@@ -1609,8 +1609,13 @@ static int do_umount(struct mount *mnt, int flags)
+
+ namespace_lock();
+ lock_mount_hash();
+- event++;
+
++ /* Recheck MNT_LOCKED with the locks held */
++ retval = -EINVAL;
++ if (mnt->mnt.mnt_flags & MNT_LOCKED)
++ goto out;
++
++ event++;
+ if (flags & MNT_DETACH) {
+ if (!list_empty(&mnt->mnt_list))
+ umount_tree(mnt, UMOUNT_PROPAGATE);
+@@ -1624,6 +1629,7 @@ static int do_umount(struct mount *mnt, int flags)
+ retval = 0;
+ }
+ }
++out:
+ unlock_mount_hash();
+ namespace_unlock();
+ return retval;
+@@ -1714,7 +1720,7 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
+ goto dput_and_out;
+ if (!check_mnt(mnt))
+ goto dput_and_out;
+- if (mnt->mnt.mnt_flags & MNT_LOCKED)
++ if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */
+ goto dput_and_out;
+ retval = -EPERM;
+ if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
+--
+2.11.0
+
--- /dev/null
+From 37b0e20be5149d5dc049e2aed3e8b03589a6ffa0 Mon Sep 17 00:00:00 2001
+From: "Eric W. Biederman" <ebiederm@xmission.com>
+Date: Tue, 13 Nov 2018 07:44:38 +0000
+Subject: [PATCH 11/11] mount: Don't allow copying MNT_UNBINDABLE|MNT_LOCKED
+ mounts
+
+BugLink: https://launchpad.net/bugs/1789161
+
+Jonathan Calmels from NVIDIA reported that he's able to bypass the
+mount visibility security check in place in the Linux kernel by using
+a combination of the unbindable property along with the private mount
+propagation option to allow a unprivileged user to see a path which
+was purposefully hidden by the root user.
+
+Reproducer:
+ # Hide a path to all users using a tmpfs
+ root@castiana:~# mount -t tmpfs tmpfs /sys/devices/
+ root@castiana:~#
+
+ # As an unprivileged user, unshare user namespace and mount namespace
+ stgraber@castiana:~$ unshare -U -m -r
+
+ # Confirm the path is still not accessible
+ root@castiana:~# ls /sys/devices/
+
+ # Make /sys recursively unbindable and private
+ root@castiana:~# mount --make-runbindable /sys
+ root@castiana:~# mount --make-private /sys
+
+ # Recursively bind-mount the rest of /sys over to /mnnt
+ root@castiana:~# mount --rbind /sys/ /mnt
+
+ # Access our hidden /sys/device as an unprivileged user
+ root@castiana:~# ls /mnt/devices/
+ breakpoint cpu cstate_core cstate_pkg i915 intel_pt isa kprobe
+ LNXSYSTM:00 msr pci0000:00 platform pnp0 power software system
+ tracepoint uncore_arb uncore_cbox_0 uncore_cbox_1 uprobe virtual
+
+Solve this by teaching copy_tree to fail if a mount turns out to be
+both unbindable and locked.
+
+Cc: stable@vger.kernel.org
+Fixes: 5ff9d8a65ce8 ("vfs: Lock in place mounts from more privileged users")
+Reported-by: Jonathan Calmels <jcalmels@nvidia.com>
+Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
+(cherry picked from commit df7342b240185d58d3d9665c0bbf0a0f5570ec29)
+Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
+Acked-by: Colin King <colin.king@canonical.com>
+Acked-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
+Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
+---
+ fs/namespace.c | 10 ++++++++--
+ 1 file changed, 8 insertions(+), 2 deletions(-)
+
+diff --git a/fs/namespace.c b/fs/namespace.c
+index dcf107925150..91a3040f0cd0 100644
+--- a/fs/namespace.c
++++ b/fs/namespace.c
+@@ -1798,8 +1798,14 @@ struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
+ for (s = r; s; s = next_mnt(s, r)) {
+ if (!(flag & CL_COPY_UNBINDABLE) &&
+ IS_MNT_UNBINDABLE(s)) {
+- s = skip_mnt_tree(s);
+- continue;
++ if (s->mnt.mnt_flags & MNT_LOCKED) {
++ /* Both unbindable and locked. */
++ q = ERR_PTR(-EPERM);
++ goto out;
++ } else {
++ s = skip_mnt_tree(s);
++ continue;
++ }
+ }
+ if (!(flag & CL_COPY_MNT_NS_FILE) &&
+ is_mnt_ns_file(s->mnt.mnt_root)) {
+--
+2.11.0
+
projects / pve-kernel.git / commitdiff