[SRU][N/M/J/F][PATCH 1/1] binder: check offset alignment in binder_get_object()

[Bethany Jamison]

From: Carlos Llamas <cmllamas at google.com>

commit aaef73821a3b0194a01bd23ca77774f704a04d40 upstream.

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.

Fixes: 6d98eb95b450 ("binder: avoid potential data leakage when copying txn")
Cc: stable at vger.kernel.org
Signed-off-by: Carlos Llamas <cmllamas at google.com>
Acked-by: Todd Kjos <tkjos at google.com>
Link: https://lore.kernel.org/r/20240330190115.1877819-1-cmllamas@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
(cherry picked from commit f01d6619045704d78613b14e2e0420bfdb7f1c15 linux-6.8.y)
CVE-2024-26926
Signed-off-by: Bethany Jamison <bethany.jamison at canonical.com>
---
 drivers/android/binder.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 5da5792ca23ff..f9043d74a19f9 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -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;
-- 
2.34.1