Patch "libnvdimm: fix reconfig_mutex, mmap_sem, and jbd2_handle lockdep splat" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

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

    libnvdimm: fix reconfig_mutex, mmap_sem, and jbd2_handle lockdep splat

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:
     libnvdimm-fix-reconfig_mutex-mmap_sem-and-jbd2_handle-lockdep-splat.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 <stable@vger.kernel.org> know about it.


>From 0beb2012a1722633515c8aaa263c73449636c893 Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@intel.com>
Date: Fri, 7 Apr 2017 09:47:24 -0700
Subject: libnvdimm: fix reconfig_mutex, mmap_sem, and jbd2_handle lockdep splat

From: Dan Williams <dan.j.williams@intel.com>

commit 0beb2012a1722633515c8aaa263c73449636c893 upstream.

Holding the reconfig_mutex over a potential userspace fault sets up a
lockdep dependency chain between filesystem-DAX and the libnvdimm ioctl
path. Move the user access outside of the lock.

     [ INFO: possible circular locking dependency detected ]
     4.11.0-rc3+ #13 Tainted: G        W  O
     -------------------------------------------------------
     fallocate/16656 is trying to acquire lock:
      (&nvdimm_bus->reconfig_mutex){+.+.+.}, at: [<ffffffffa00080b1>] nvdimm_bus_lock+0x21/0x30 [libnvdimm]
     but task is already holding lock:
      (jbd2_handle){++++..}, at: [<ffffffff813b4944>] start_this_handle+0x104/0x460

    which lock already depends on the new lock.

    the existing dependency chain (in reverse order) is:

    -> #2 (jbd2_handle){++++..}:
            lock_acquire+0xbd/0x200
            start_this_handle+0x16a/0x460
            jbd2__journal_start+0xe9/0x2d0
            __ext4_journal_start_sb+0x89/0x1c0
            ext4_dirty_inode+0x32/0x70
            __mark_inode_dirty+0x235/0x670
            generic_update_time+0x87/0xd0
            touch_atime+0xa9/0xd0
            ext4_file_mmap+0x90/0xb0
            mmap_region+0x370/0x5b0
            do_mmap+0x415/0x4f0
            vm_mmap_pgoff+0xd7/0x120
            SyS_mmap_pgoff+0x1c5/0x290
            SyS_mmap+0x22/0x30
            entry_SYSCALL_64_fastpath+0x1f/0xc2

    -> #1 (&mm->mmap_sem){++++++}:
            lock_acquire+0xbd/0x200
            __might_fault+0x70/0xa0
            __nd_ioctl+0x683/0x720 [libnvdimm]
            nvdimm_ioctl+0x8b/0xe0 [libnvdimm]
            do_vfs_ioctl+0xa8/0x740
            SyS_ioctl+0x79/0x90
            do_syscall_64+0x6c/0x200
            return_from_SYSCALL_64+0x0/0x7a

    -> #0 (&nvdimm_bus->reconfig_mutex){+.+.+.}:
            __lock_acquire+0x16b6/0x1730
            lock_acquire+0xbd/0x200
            __mutex_lock+0x88/0x9b0
            mutex_lock_nested+0x1b/0x20
            nvdimm_bus_lock+0x21/0x30 [libnvdimm]
            nvdimm_forget_poison+0x25/0x50 [libnvdimm]
            nvdimm_clear_poison+0x106/0x140 [libnvdimm]
            pmem_do_bvec+0x1c2/0x2b0 [nd_pmem]
            pmem_make_request+0xf9/0x270 [nd_pmem]
            generic_make_request+0x118/0x3b0
            submit_bio+0x75/0x150

Fixes: 62232e45f4a2 ("libnvdimm: control (ioctl) messages for nvdimm_bus and nvdimm devices")
Cc: Dave Jiang <dave.jiang@intel.com>
Reported-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/nvdimm/bus.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/nvdimm/bus.c
+++ b/drivers/nvdimm/bus.c
@@ -934,8 +934,14 @@ static int __nd_ioctl(struct nvdimm_bus
 	rc = nd_desc->ndctl(nd_desc, nvdimm, cmd, buf, buf_len, NULL);
 	if (rc < 0)
 		goto out_unlock;
+	nvdimm_bus_unlock(&nvdimm_bus->dev);
+
 	if (copy_to_user(p, buf, buf_len))
 		rc = -EFAULT;
+
+	vfree(buf);
+	return rc;
+
  out_unlock:
 	nvdimm_bus_unlock(&nvdimm_bus->dev);
  out:


Patches currently in stable-queue which might be from dan.j.williams@intel.com are

queue-4.9/acpi-nfit-libnvdimm-fix-interleave-set-cookie-calculation-64-bit-comparison.patch
queue-4.9/libnvdimm-fix-blk-free-space-accounting.patch
queue-4.9/x86-pmem-fix-broken-__copy_user_nocache-cache-bypass-assumptions.patch
queue-4.9/libnvdimm-fix-reconfig_mutex-mmap_sem-and-jbd2_handle-lockdep-splat.patch