binder: check offset alignment in binder_get_object()

mainline inclusion
from mainline-v6.9-rc5
commit aaef73821a3b0194a01bd23ca77774f704a04d40
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9JJ2F
CVE: CVE-2024-26926

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=aaef73821a3b0194a01bd23ca77774f704a04d40



--------------------------------

Commit 6d98eb95 ("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 7a67a393
("binder: add function to copy binder object from buffer"), likely
removed due to redundancy at the time.

Fixes: 6d98eb95 ("binder: avoid potential data leakage when copying txn")
Cc: stable@vger.kernel.org
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Acked-by: Todd Kjos <tkjos@google.com>
Link: https://lore.kernel.org/r/20240330190115.1877819-1-cmllamas@google.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Lin Yujun <linyujun809@huawei.com>