| 74c9983e80d8224bbe1de7c37e8f6ac4a76df11d |
|
06-Dec-2016 |
Svetoslav Ganov <svetoslavganov@google.com> |
Fix vulnerability in MemoryIntArray
MemoryIntArray was using the size of the undelying
ashmem region to mmap the data but the ashmem size
can be changed until the former is memory mapped.
Since we use the ashmem region size for boundary
checking and memory unmapping if it does not match
the size used while mapping an attacker can force
the system to unmap memory or to access undefined
memory and crash.
Also we were passing the memory address where the
ashmem region is mapped in the owner process to
support cases where the client can pass back the
MemoryIntArray instance. This allows an attacker
to put invalid address and cause arbitrary memory
to be freed.
Now we no longer support passing back the instance
to the owner process (the passed back instance is
read only), so no need to pass the memory adress
of the owner's mapping, thus not allowing freeing
arbitrary memory.
Further, we now check the memory mapped size against
the size of the underlying ashmem region after we do
the memory mapping (to fix the ahsmem size) and if
an attacker changed the size under us we throw.
Tests: Updated the tests and they pass.
bug:33039926
bug:33042690
Change-Id: Ib8e50afcdb5475123968572ac9696e8ed4031631
/frameworks/base/packages/SettingsProvider/src/com/android/providers/settings/GenerationRegistry.java
|
| 9d723d3d573a53173bd8210be20f0ec622eef8fd |
|
27-Aug-2016 |
Svet Ganov <svetoslavganov@google.com> |
Polish MemoryIntArray
1. Add close guard
2. Adopt instead of clone the ahsmem fd to fix a dangling fd
3. Clear only the return flag when writing fd to parcel
4. Immediately destroy remote MemoryIntArray if stale
5. Throw Java exception if someone closed the fd under us
Change-Id: I85533fec336c40e3380e10d5448e18c9616ec341
/frameworks/base/packages/SettingsProvider/src/com/android/providers/settings/GenerationRegistry.java
|
| 8c35dcc7ae956394a6513f4ced8359f56260fbc4 |
|
18-Jun-2016 |
Svetoslav Ganov <svetoslavganov@google.com> |
Fix a race in local settings caches
We send a handle to the generation tracker along with the first accessed
setting but don't send the generation id of when the setting was
actually looked up. So by the time the client gets the setting with the
generation tracker from which to get and cache the last generation the
setting may have changed. We need to pass the generation id along with
the value and the generation tracker.
bug:29458487
Change-Id: I0ac4955ba5b10b547f8fe653a7c28e048a4691eb
/frameworks/base/packages/SettingsProvider/src/com/android/providers/settings/GenerationRegistry.java
|
| 04df738bcb6584dd82b731a67f4cf8d6925b061e |
|
11-May-2016 |
Svetoslav Ganov <svetoslavganov@google.com> |
Make settings cahches generation mechanism robust.
Settings is using a MemoryIntArray to communicate the settings table
version enabling apps to have up-to-date local caches. However, ashmem
allows an arbitrary process with a handle to the fd (even in read only
mode) to unpin the memory which can then be garbage collected. Here we
make this mechanism fault tolerant against bad apps unpinning the ashmem
region. First, we no longer unpin the ashmem on the client side and if
the ashmem region is purged and cannot be pinned we recreate it and
hook up again with the local app caches. The change also adds a test
that clients can only read while owner can read/write.
bug:28764789
Change-Id: I1ef79b4b21e976124b268c9126a55d614157059b
/frameworks/base/packages/SettingsProvider/src/com/android/providers/settings/GenerationRegistry.java
|
| 53a441ca8eda5a3e6209a952b1bbd32a39e19a1c |
|
20-Apr-2016 |
Svet Ganov <svetoslavganov@google.com> |
Ensure local settings caches are not stale
We used the system proterties as a shared memory mechanism
to propagate information to local settings caches when the
content has changed and the cache should be cleared. The
system properties are unfortunately updated asynchronously
leading to cases where clients may read stale data.
This change adds a simple int array data structure backed
by shared memory which guarantees individual values are
atomically read and updated without memory tear. Multi-
index opearations are not synchronized between each other.
The settings provider is using the new data structure to
propagate the settings generation which drives when caches
are purged.
We have a single memory array keeping the generation for
different settings tables per user. Since memory array is
not a compact data structure and the user space exceeds
the memory array size we use an in-memory map from keys
to indices in the memory array where the generation id of
a key is stored. A key is derived by the setting type in
the 4 most significant bits and the user id in the 28 least
significant bits.
The mapping from a key to an index is cleared if the user is
removed and the corresponding index in the memory arry is
reset to make it available for other users. The size of the
memory array is derived from the max user count that can be
created at the same time.
bug:18826179
Change-Id: I64009cc5105309ef9aa83aba90b82afc8ad8c659
/frameworks/base/packages/SettingsProvider/src/com/android/providers/settings/GenerationRegistry.java
|