CVE-2024-26926: binder: check offset alignment in binder_get_object()

CVE-2024-26926: binder: check offset alignment in binder_get_object()

[Lee Jones]

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

binder: check offset alignment in binder_get_object()

Commit 6d98eb95b450 ("binder: avoid potential data leakage when copying
txn") introduced changes to how binder objects are copied. In doing so,
it unintentionally removed an offset alignment check done through calls
to binder_alloc_copy_from_buffer() -> check_buffer().

These calls were replaced in binder_get_object() with copy_from_user(),
so now an explicit offset alignment check is needed here. This avoids
later complications when unwinding the objects gets harder.

It is worth noting this check existed prior to commit 7a67a39320df
("binder: add function to copy binder object from buffer"), likely
removed due to redundancy at the time.

The Linux kernel CVE team has assigned CVE-2024-26926 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.17 with commit 6d98eb95b450 and fixed in 6.9-rc5 with commit aaef73821a3b
	Issue introduced in 5.4.226 with commit c056a6ba35e0
	Issue introduced in 5.10.157 with commit 23e9d815fad8
	Issue introduced in 5.15.17 with commit 7a9ad4aceb02
	Issue introduced in 5.16.3 with commit 66e12f5b3a97

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-26926
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/android/binder.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/aaef73821a3b0194a01bd23ca77774f704a04d40