linux-cve-announce - CVE-2024-26806: spi: cadence-qspi: remove system-wide suspend helper calls from runtime PM hooks

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Date: Thu,  4 Apr 2024 10:23:23 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-26806: spi: cadence-qspi: remove system-wide suspend helper calls from runtime PM hooks

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

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

spi: cadence-qspi: remove system-wide suspend helper calls from runtime PM hooks

The ->runtime_suspend() and ->runtime_resume() callbacks are not
expected to call spi_controller_suspend() and spi_controller_resume().
Remove calls to those in the cadence-qspi driver.

Those helpers have two roles currently:
 - They stop/start the queue, including dealing with the kworker.
 - They toggle the SPI controller SPI_CONTROLLER_SUSPENDED flag. It
   requires acquiring ctlr->bus_lock_mutex.

Step one is irrelevant because cadence-qspi is not queued. Step two
however has two implications:
 - A deadlock occurs, because ->runtime_resume() is called in a context
   where the lock is already taken (in the ->exec_op() callback, where
   the usage count is incremented).
 - It would disallow all operations once the device is auto-suspended.

Here is a brief call tree highlighting the mutex deadlock:

spi_mem_exec_op()
        ...
        spi_mem_access_start()
                mutex_lock(&ctlr->bus_lock_mutex)

        cqspi_exec_mem_op()
                pm_runtime_resume_and_get()
                        cqspi_resume()
                                spi_controller_resume()
                                        mutex_lock(&ctlr->bus_lock_mutex)
                ...

        spi_mem_access_end()
                mutex_unlock(&ctlr->bus_lock_mutex)
        ...

The Linux kernel CVE team has assigned CVE-2024-26806 to this issue.


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

	Issue introduced in 6.7 with commit 0578a6dbfe75 and fixed in 6.7.9 with commit 041562ebc475
	Issue introduced in 6.7 with commit 0578a6dbfe75 and fixed in 6.8 with commit 959043afe53a

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-2024-26806
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/spi/spi-cadence-quadspi.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/041562ebc4759c9932b59a06527f8753b86da365
	https://git.kernel.org/stable/c/959043afe53ae80633e810416cee6076da6e91c6