staging/android/ion : fix a race condition in the ion driver
authorEunTaik Lee <eun.taik.lee@samsung.com>
Wed, 24 Feb 2016 04:38:06 +0000 (04:38 +0000)
committerWinnie Hsu <whsu@nvidia.com>
Thu, 19 Apr 2018 17:02:37 +0000 (10:02 -0700)
commit5b4cd8a02591e224104ae4fce3a569b48c42c0ad
treecdd29a7e6ac72d440eec4f445efa06b89d0fff0d
parent9dca2d2a8e0fff7601f28fd037d1386ff2cbe4df
staging/android/ion : fix a race condition in the ion driver

There is a use-after-free problem in the ion driver.
This is caused by a race condition in the ion_ioctl()
function.

A handle has ref count of 1 and two tasks on different
cpus calls ION_IOC_FREE simultaneously.

cpu 0                                   cpu 1
-------------------------------------------------------
ion_handle_get_by_id()
(ref == 2)
                            ion_handle_get_by_id()
                            (ref == 3)

ion_free()
(ref == 2)

ion_handle_put()
(ref == 1)

                            ion_free()
                            (ref == 0 so ion_handle_destroy() is
                            called
                            and the handle is freed.)

                            ion_handle_put() is called and it
                            decreases the slub's next free pointer

The problem is detected as an unaligned access in the
spin lock functions since it uses load exclusive
 instruction. In some cases it corrupts the slub's
free pointer which causes a mis-aligned access to the
next free pointer.(kmalloc returns a pointer like
ffffc0745b4580aa). And it causes lots of other
hard-to-debug problems.

This symptom is caused since the first member in the
ion_handle structure is the reference count and the
ion driver decrements the reference after it has been
freed.

To fix this problem client->lock mutex is extended
to protect all the codes that uses the handle.

Bug 1836932

Change-Id: I45abd9dd1f696105a7840a25ba4a594b5af4fa65
Signed-off-by: Eun Taik Lee <eun.taik.lee@samsung.com>
Reviewed-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Gagan Grover <ggrover@nvidia.com>
Reviewed-on: http://git-master/r/1260541
(cherry picked from commit cde60b4e09dcff7942ab9bd703c435d5b62dd104)
Reviewed-on: https://git-master.nvidia.com/r/1694046
GVS: Gerrit_Virtual_Submit
Reviewed-by: Prabhu Kuttiyam <pkuttiyam@nvidia.com>
Tested-by: Amulya Yarlagadda <ayarlagadda@nvidia.com>
Reviewed-by: Winnie Hsu <whsu@nvidia.com>
drivers/staging/android/ion/ion.c [changed mode: 0644->0755]