linux-kernel - [PATCH 4.9 67/84] Revert "android: binder: Sanity check at binder ioctl"

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Date:   Mon, 28 Aug 2017 10:05:32 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Todd Kjos <tkjos@...gle.com>
Subject: [PATCH 4.9 67/84] Revert "android: binder: Sanity check at binder ioctl"

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Todd Kjos <tkjos@...roid.com>

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.

Signed-off-by: Todd Kjos <tkjos@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -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);