patch "Revert "android: binder: Sanity check at binder ioctl"" added to char-misc-next

[<gregkh@linuxfoundation.org>]

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 my char-misc git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-next branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release
during the merge window.

If you have any questions about this process, please let me know.


>From a2b18708ee14baec4ef9c0fba96070bba14d0081 Mon Sep 17 00:00:00 2001
From: Todd Kjos <tkjos@android.com>
Date: Wed, 5 Jul 2017 13:46:01 -0700
Subject: 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.

Signed-off-by: Todd Kjos <tkjos@google.com>
Cc: stable <stable@vger.kernel.org> # 4.6+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/android/binder.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index aae4d8d4be36..157bd3e49ff4 100644
--- 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);
 	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);
-- 
2.13.3