cve/published/2022/CVE-2022-49300.mbox

From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: <linux-cve-announce@vger.kernel.org>
Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org>
Subject: CVE-2022-49300: nbd: fix race between nbd_alloc_config() and module removal

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

nbd: fix race between nbd_alloc_config() and module removal

When nbd module is being removing, nbd_alloc_config() may be
called concurrently by nbd_genl_connect(), although try_module_get()
will return false, but nbd_alloc_config() doesn't handle it.

The race may lead to the leak of nbd_config and its related
resources (e.g, recv_workq) and oops in nbd_read_stat() due
to the unload of nbd module as shown below:

  BUG: kernel NULL pointer dereference, address: 0000000000000040
  Oops: 0000 [#1] SMP PTI
  CPU: 5 PID: 13840 Comm: kworker/u17:33 Not tainted 5.14.0+ #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
  Workqueue: knbd16-recv recv_work [nbd]
  RIP: 0010:nbd_read_stat.cold+0x130/0x1a4 [nbd]
  Call Trace:
   recv_work+0x3b/0xb0 [nbd]
   process_one_work+0x1ed/0x390
   worker_thread+0x4a/0x3d0
   kthread+0x12a/0x150
   ret_from_fork+0x22/0x30

Fixing it by checking the return value of try_module_get()
in nbd_alloc_config(). As nbd_alloc_config() may return ERR_PTR(-ENODEV),
assign nbd->config only when nbd_alloc_config() succeeds to ensure
the value of nbd->config is binary (valid or NULL).

Also adding a debug message to check the reference counter
of nbd_config during module removal.

The Linux kernel CVE team has assigned CVE-2022-49300 to this issue.


Affected and fixed versions
===========================

	Fixed in 4.14.283 with commit 165cf2e0019fa6cedc75b456490c41494c34abb4
	Fixed in 4.19.247 with commit 2573f2375b64280be977431701ed5d33b75b9ad0
	Fixed in 5.4.198 with commit 8a7da4ced236ce6637fe70f14ca18e718d4bf9e9
	Fixed in 5.10.122 with commit 122e4adaff2439f1cc18cc7e931980fa7560df5c
	Fixed in 5.15.47 with commit 71c142f910da44421213ade601bcbd23ceae19fa
	Fixed in 5.17.15 with commit 2888fa41985f93ed0a6837cfbb06bcbfd7fa2314
	Fixed in 5.18.4 with commit d09525720dd5201756f698bee1076de9aefd4602
	Fixed in 5.19 with commit c55b2b983b0fa012942c3eb16384b2b722caa810

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2022-49300
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/block/nbd.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/165cf2e0019fa6cedc75b456490c41494c34abb4
	https://git.kernel.org/stable/c/2573f2375b64280be977431701ed5d33b75b9ad0
	https://git.kernel.org/stable/c/8a7da4ced236ce6637fe70f14ca18e718d4bf9e9
	https://git.kernel.org/stable/c/122e4adaff2439f1cc18cc7e931980fa7560df5c
	https://git.kernel.org/stable/c/71c142f910da44421213ade601bcbd23ceae19fa
	https://git.kernel.org/stable/c/2888fa41985f93ed0a6837cfbb06bcbfd7fa2314
	https://git.kernel.org/stable/c/d09525720dd5201756f698bee1076de9aefd4602
	https://git.kernel.org/stable/c/c55b2b983b0fa012942c3eb16384b2b722caa810