Patch "Revert "android: binder: Sanity check at binder ioctl"" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

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

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
revert-android-binder-sanity-check-at-binder-ioctl.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Todd Kjos <[email protected]>
Date: Wed, 5 Jul 2017 13:46:01 -0700
Subject: Revert "android: binder: Sanity check at binder ioctl"

From: Todd Kjos <[email protected]>

commit a2b18708ee14baec4ef9c0fba96070bba14d0081 upstream.

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.

---
 drivers/android/binder.c |    5 -----
 1 file changed, 5 deletions(-)

@@ -2760,10 +2760,6 @@ static long binder_ioctl(struct file *fi
 	/*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);

@@ -2978,7 +2974,6 @@ static int binder_open(struct inode *nod
 		return -ENOMEM;
 	get_task_struct(current);
 	proc->tsk = current;
-	proc->vma_vm_mm = current->mm;
 	INIT_LIST_HEAD(&proc->todo);
 	init_waitqueue_head(&proc->wait);
 	proc->default_priority = task_nice(current);

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/binder-use-group-leader-instead-of-open-thread.patch queue-4.9/revert-android-binder-sanity-check-at-binder-ioctl.patch