android: binder: More offset validation.

Make sure offsets don't point to overlapping flat_binder_object
structs.

Change-Id: I85c759b9c6395492474b177625dc6b0b289fd6b0
Signed-off-by: Arve Hjønnevåg <arve@android.com>

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 52aae90eb1fd7a862a94106021c80d2002fee487..b9242c6905baafdd0c42d5b556a25891198eec80 100644 (file)
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -1322,6 +1322,7 @@ static void binder_transaction(struct binder_proc *proc,
        struct binder_transaction *t;
        struct binder_work *tcomplete;
        binder_size_t *offp, *off_end;
+       binder_size_t off_min;
        struct binder_proc *target_proc;
        struct binder_thread *target_thread = NULL;
        struct binder_node *target_node = NULL;
@@ -1518,18 +1519,24 @@ static void binder_transaction(struct binder_proc *proc,
                goto err_bad_offset;
        }
        off_end = (void *)offp + tr->offsets_size;
+       off_min = 0;
        for (; offp < off_end; offp++) {
                struct flat_binder_object *fp;
 
                if (*offp > t->buffer->data_size - sizeof(*fp) ||
+                   *offp < off_min ||
                    t->buffer->data_size < sizeof(*fp) ||
                    !IS_ALIGNED(*offp, sizeof(u32))) {
-                       binder_user_error("%d:%d got transaction with invalid offset, %lld\n",
-                                         proc->pid, thread->pid, (u64)*offp);
+                       binder_user_error("%d:%d got transaction with invalid offset, %lld (min %lld, max %lld)\n",
+                                         proc->pid, thread->pid, (u64)*offp,
+                                         (u64)off_min,
+                                         (u64)(t->buffer->data_size -
+                                         sizeof(*fp)));
                        return_error = BR_FAILED_REPLY;
                        goto err_bad_offset;
                }
                fp = (struct flat_binder_object *)(t->buffer->data + *offp);
+               off_min = *offp + sizeof(struct flat_binder_object);
                switch (fp->type) {
                case BINDER_TYPE_BINDER:
                case BINDER_TYPE_WEAK_BINDER: {