Subject: CVE-2022-48658: mm: slub: fix flush_cpu_slab()/__free_slab() invocations in task context.

From: Greg Kroah-Hartman <[email-masked]>

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

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

mm: slub: fix flush_cpu_slab()/__free_slab() invocations in task context.

Commit 5a836bf6b09f ("mm: slub: move flush_cpu_slab() invocations
__free_slab() invocations out of IRQ context") moved all flush_cpu_slab()
invocations to the global workqueue to avoid a problem related
with deactivate_slab()/__free_slab() being called from an IRQ context
on PREEMPT_RT kernels.

When the flush_all_cpu_locked() function is called from a task context
it may happen that a workqueue with WQ_MEM_RECLAIM bit set ends up
flushing the global workqueue, this will cause a dependency issue.

 workqueue: WQ_MEM_RECLAIM nvme-delete-wq:nvme_delete_ctrl_work [nvme_core]
   is flushing !WQ_MEM_RECLAIM events:flush_cpu_slab
 WARNING: CPU: 37 PID: 410 at kernel/workqueue.c:2637
   check_flush_dependency+0x10a/0x120
 Workqueue: nvme-delete-wq nvme_delete_ctrl_work [nvme_core]
 RIP: 0010:check_flush_dependency+0x10a/0x120[  453.262125] Call Trace:
 __flush_work.isra.0+0xbf/0x220
 ? __queue_work+0x1dc/0x420
 flush_all_cpus_locked+0xfb/0x120
 __kmem_cache_shutdown+0x2b/0x320
 kmem_cache_destroy+0x49/0x100
 bioset_exit+0x143/0x190
 blk_release_queue+0xb9/0x100
 kobject_cleanup+0x37/0x130
 nvme_fc_ctrl_free+0xc6/0x150 [nvme_fc]
 nvme_free_ctrl+0x1ac/0x2b0 [nvme_core]

Fix this bug by creating a workqueue for the flush operation with
the WQ_MEM_RECLAIM bit set.

The Linux kernel CVE team has assigned CVE-2022-48658 to this issue.

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

	Issue introduced in 5.15 with commit 5a836bf6b09f and fixed in 5.15.71 with commit 61703b248be9
	Issue introduced in 5.15 with commit 5a836bf6b09f and fixed in 5.19.12 with commit df6cb39335cf
	Issue introduced in 5.15 with commit 5a836bf6b09f and fixed in 6.0 with commit e45cc288724f

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-2022-48658
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:
	mm/slub.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/61703b248be993eb4997b00ae5d3318e6d8f3c5b
	https://git.kernel.org/stable/c/df6cb39335cf5a1b918e8dbd8ba7cd9f1d00e45a
	https://git.kernel.org/stable/c/e45cc288724f0cfd497bb5920bcfa60caa335729