Subject: CVE-2024-35991: dmaengine: idxd: Convert spinlock to mutex to lock evl workqueue

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

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

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

dmaengine: idxd: Convert spinlock to mutex to lock evl workqueue

drain_workqueue() cannot be called safely in a spinlocked context due to
possible task rescheduling. In the multi-task scenario, calling
queue_work() while drain_workqueue() will lead to a Call Trace as
pushing a work on a draining workqueue is not permitted in spinlocked
context.
    Call Trace:
    <TASK>
    ? __warn+0x7d/0x140
    ? __queue_work+0x2b2/0x440
    ? report_bug+0x1f8/0x200
    ? handle_bug+0x3c/0x70
    ? exc_invalid_op+0x18/0x70
    ? asm_exc_invalid_op+0x1a/0x20
    ? __queue_work+0x2b2/0x440
    queue_work_on+0x28/0x30
    idxd_misc_thread+0x303/0x5a0 [idxd]
    ? __schedule+0x369/0xb40
    ? __pfx_irq_thread_fn+0x10/0x10
    ? irq_thread+0xbc/0x1b0
    irq_thread_fn+0x21/0x70
    irq_thread+0x102/0x1b0
    ? preempt_count_add+0x74/0xa0
    ? __pfx_irq_thread_dtor+0x10/0x10
    ? __pfx_irq_thread+0x10/0x10
    kthread+0x103/0x140
    ? __pfx_kthread+0x10/0x10
    ret_from_fork+0x31/0x50
    ? __pfx_kthread+0x10/0x10
    ret_from_fork_asm+0x1b/0x30
    </TASK>

The current implementation uses a spinlock to protect event log workqueue
and will lead to the Call Trace due to potential task rescheduling.

To address the locking issue, convert the spinlock to mutex, allowing
the drain_workqueue() to be called in a safe mutex-locked context.

This change ensures proper synchronization when accessing the event log
workqueue, preventing potential Call Trace and improving the overall
robustness of the code.

The Linux kernel CVE team has assigned CVE-2024-35991 to this issue.

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

	Issue introduced in 6.4 with commit c40bd7d9737b and fixed in 6.6.30 with commit 758071a35d9f
	Issue introduced in 6.4 with commit c40bd7d9737b and fixed in 6.8.9 with commit c9b732a9f73e
	Issue introduced in 6.4 with commit c40bd7d9737b and fixed in 6.9 with commit d5638de827cf

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-2024-35991
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/dma/idxd/cdev.c
	drivers/dma/idxd/debugfs.c
	drivers/dma/idxd/device.c
	drivers/dma/idxd/idxd.h
	drivers/dma/idxd/init.c
	drivers/dma/idxd/irq.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/758071a35d9f3ffd84ff12169d081412a2f5f098
	https://git.kernel.org/stable/c/c9b732a9f73eadc638abdcf0a6d39bc7a0c1af5f
	https://git.kernel.org/stable/c/d5638de827cff0fce77007e426ec0ffdedf68a44