Revert "android: binder: Sanity check at binder ioctl"

This reverts commit a906d6931f3ccaf7de805643190765ddd7378e27.

The patch introduced a race in the binder driver. An attempt to fix the
race was submitted in "[PATCH v2] android: binder: fix dangling pointer
comparison", however the conclusion in the discussion for that patch
was that the original patch should be reverted.

The reversion is being done as part of the fine-grained locking
patchset since the patch would need to be refactored when
proc->vmm_vm_mm is removed from struct binder_proc and added
in the binder allocator.

Also needs reversion in 4.9 LTS

Change-Id: I9777ece955c07ac30432187bb968f87cf73271d8
Signed-off-by: Todd Kjos <tkjos@google.com>

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 6e85c79cf9f808f3af3d40269b6ea22de48071a7..9105f416ce463d6180453ffb4f7f842aa0cc0c32 100644 (file)
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -3247,10 +3247,6 @@ static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
        /*pr_info("binder_ioctl: %d:%d %x %lx\n",
                        proc->pid, current->pid, cmd, arg);*/
 
-       if (unlikely(current->mm != proc->vma_vm_mm)) {
-               pr_err("current mm mismatch proc mm\n");
-               return -EINVAL;
-       }
        trace_binder_ioctl(cmd, arg);
 
        ret = wait_event_interruptible(binder_user_error_wait, binder_stop_on_user_error < 2);
@@ -3466,7 +3462,6 @@ static int binder_open(struct inode *nodp, struct file *filp)
                return -ENOMEM;
        get_task_struct(current->group_leader);
        proc->tsk = current->group_leader;
-       proc->vma_vm_mm = current->group_leader->mm;
        INIT_LIST_HEAD(&proc->todo);
        init_waitqueue_head(&proc->wait);
        proc->default_priority = task_nice(current);