android: binder: More offset validation

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

Cc: Colin Cross <ccross@android.com>
Cc: Arve Hjønnevåg <arve@android.com>
Cc: Dmitry Shmidt <dimitrysh@google.com>
Cc: Rom Lemarchand <romlem@google.com>
Cc: Serban Constantinescu <serban.constantinescu@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Android Kernel Team <kernel-team@android.com>
Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 9 insertions, 2 deletions

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index a39e85f9efa9..1db376184955 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -1321,6 +1321,7 @@ 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;
@@ -1522,18 +1523,24 @@ 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: {