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FROMLIST: binder: check offset alignment in binder_get_object()

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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>
Acked-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>

Bug: 320661088
Link: https://lore.kernel.org/all/20240330190115.1877819-1-cmllamas@google.com/
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Change-Id: Iaddabaa28de7ba7b7d35dbb639d38ca79dbc5077
(cherry picked from commit 0c9784b747)
Signed-off-by: Lee Jones <joneslee@google.com>
This commit is contained in:
Carlos Llamas 2024-03-30 19:01:14 +00:00 committed by Lee Jones
parent 337a4a7d36
commit 5e5adb0e04
1 changed files with 3 additions and 1 deletions
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4
drivers/android/binder.c
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@ -1891,8 +1891,10 @@ 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;