CVE-2026-64501: iio: adc: ad_sigma_delta: fix CS held asserted and state leaks

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

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

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

iio: adc: ad_sigma_delta: fix CS held asserted and state leaks

In ad_sigma_delta_single_conversion(), set_mode(AD_SD_MODE_IDLE) and
disable_one() were called from the out: block while keep_cs_asserted
was still true. This caused any SPI transfer issued by those callbacks
to carry cs_change=1, leaving CS permanently asserted after the
conversion. Fix by moving both calls into the out_unlock: block, after
keep_cs_asserted is cleared, matching the pattern already used in
ad_sd_calibrate().

In the error path of ad_sd_buffer_postenable(), if an operation fails
after set_mode(AD_SD_MODE_CONTINUOUS) has already succeeded (e.g.
spi_offload_trigger_enable()), the device is left in continuous
conversion mode with CS physically asserted. Additionally,
bus_locked remaining true after spi_bus_unlock() causes subsequent
SPI operations to call spi_sync_locked() without the bus lock actually
held, allowing concurrent SPI access.

Fix the error path by clearing keep_cs_asserted first, then calling
set_mode(AD_SD_MODE_IDLE) to revert the device mode and deassert CS,
then clearing bus_locked before releasing the bus.

For devices that implement neither set_mode nor disable_one (such as
MAX11205, which has no physical CS pin), no SPI transfer is issued
during cleanup and the cs_change flag has no effect on any physical
line.

The Linux kernel CVE team has assigned CVE-2026-64501 to this issue.


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

	Issue introduced in 6.14 with commit 132d44dc6966c1cf841ffe0f6f048165687e870b and fixed in 6.18.39 with commit c313bb7c38855e94ceef939d152dd75e5a904b5f
	Issue introduced in 6.14 with commit 132d44dc6966c1cf841ffe0f6f048165687e870b and fixed in 7.1.4 with commit f1de829ee87a1198d3465493ce430d36c5fa029c
	Issue introduced in 6.14 with commit 132d44dc6966c1cf841ffe0f6f048165687e870b and fixed in 7.2-rc1 with commit c72da0688575e5ef39c36bb44fed53aa18f8ae65

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-2026-64501
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/iio/adc/ad_sigma_delta.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/c313bb7c38855e94ceef939d152dd75e5a904b5f
	https://git.kernel.org/stable/c/f1de829ee87a1198d3465493ce430d36c5fa029c
	https://git.kernel.org/stable/c/c72da0688575e5ef39c36bb44fed53aa18f8ae65