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binder: check offset alignment in binder_get_object()

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commit aaef73821a upstream.

Commit 6d98eb95b4 ("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 7a67a39320
("binder: add function to copy binder object from buffer"), likely
removed due to redundancy at the time.

Fixes: 6d98eb95b4 ("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>
This commit is contained in:
Carlos Llamas 2024-03-30 19:01:14 +00:00 committed by Greg Kroah-Hartman
parent 03b8a612bf
commit f01d661904
1 changed files with 3 additions and 1 deletions
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4
drivers/android/binder.c
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@ -1708,8 +1708,10 @@ static size_t binder_get_object(struct binder_proc *proc,
size_t object_size = 0;
read_size = min_t(size_t, sizeof(*object), buffer->data_size - offset);
if (offset > buffer->data_size || read_size < sizeof(*hdr))
if (offset > buffer->data_size || read_size < sizeof(*hdr) ||
!IS_ALIGNED(offset, sizeof(u32)))
return 0;
if (u) {
if (copy_from_user(object, u + offset, read_size))
return 0;