Relabeling this for security access.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform2/+/44125df0553a4b77801dc950b5d695f0e483aa76

commit 44125df0553a4b77801dc950b5d695f0e483aa76
Author: Ben Chan <benchan@chromium.org>
Date: Fri May 26 00:15:51 2017

cros-disks: put FUSE mount programs in new mount namespace

This CL changes cros-disks to put FUSE mount programs in a new mount
namespace, which prevents mounts, so mounts inside that namespace don't
normally propagate out except when a mount is created under /media,
which is marked as a shared mount (by chromeos_startup). This prevents
the FUSE mount program from remounting an existing mount point outside
/media.

BUG= chromium:722946 
TEST=Tested the following:
1. Run platform_CrosDisksFilesystem tests.
2. Insert an NTFS formatted USB drive and verify read/write operations
   on the drive via Files.app.
3. Insert an exFAT formatted USB drive and verify read/write operations
   on the drive via Files.app.

Change-Id: I14911b965964f5d97140864d0f4c5f35952ac04e
Reviewed-on: https://chromium-review.googlesource.com/513490
Commit-Ready: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>

[modify] https://crrev.com/44125df0553a4b77801dc950b5d695f0e483aa76/cros-disks/fuse_mounter.cc
[modify] https://crrev.com/44125df0553a4b77801dc950b5d695f0e483aa76/cros-disks/sandboxed_process.cc
[modify] https://crrev.com/44125df0553a4b77801dc950b5d695f0e483aa76/cros-disks/sandboxed_process.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform2/+/0dd418890c526eb1c0e03e889cfc3d81bceb5ede

commit 0dd418890c526eb1c0e03e889cfc3d81bceb5ede
Author: Ben Chan <benchan@chromium.org>
Date: Fri May 26 00:15:51 2017

cros-disks: further restrict FUSE mount programs

This CL changes cros-disks to further restrict FUSE mount programs as
follows:
- put in new cgroup, IPC, network namespace
- set no_new_privs bit

BUG= chromium:722946 
TEST=Tested the following:
1. Run platform_CrosDisksFilesystem tests.
2. Insert an NTFS formatted USB drive and verify read/write operations
   on the drive via Files.app.
3. Insert an exFAT formatted USB drive and verify read/write operations
   on the drive via Files.app.

Change-Id: I813edeb8e2f47212ee55c1a42fb4e099ec62a284
Reviewed-on: https://chromium-review.googlesource.com/513491
Commit-Ready: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>

[modify] https://crrev.com/0dd418890c526eb1c0e03e889cfc3d81bceb5ede/cros-disks/fuse_mounter.cc
[modify] https://crrev.com/0dd418890c526eb1c0e03e889cfc3d81bceb5ede/cros-disks/sandboxed_process.cc
[modify] https://crrev.com/0dd418890c526eb1c0e03e889cfc3d81bceb5ede/cros-disks/sandboxed_process.h

Should we mark this Fixed and follow up in  issue 726036 ?

Re #4: I was looking into the issue with PID namespace, but I'll follow up on that in  issue 726036  instead (as this issue is about mount namespace)

Given that we have merged the updated exfat-fuse in M59, do we see the urgency to merge this change to M59?

I don't think we need to merge to 59.

This bug has been closed for more than 14 weeks. Removing security view restrictions.

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