CVE-2026-98677: iio: adc: ad_sigma_delta: fix use-after-free on unbind

CVE-2026-98677: iio: adc: ad_sigma_delta: fix use-after-free on unbind

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

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

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

iio: adc: ad_sigma_delta: fix use-after-free on unbind

ad_sd_buffer_postenable() allocates sigma_delta->samples_buf with
devm_krealloc() at runtime, so its devres entry sits after all
probe-time entries of the driver. devm resources are released in
reverse allocation order, which means unbind frees samples_buf before
iio_device_unregister() disables the buffers and detaches the trigger
pollfunc. The data ready IRQ is still enabled at that point, so
ad_sd_trigger_handler() can still run and memcpy() incoming samples
into the freed samples_buf.

Fix this by preallocating the buffer in
devm_ad_sd_setup_buffer_and_trigger(), before the triggered buffer and
the IRQ are set up, so it is freed only after iio_device_unregister()
has drained the trigger handler via free_irq(). Size it for the worst
case of all sequencer slots being active; ad_sd_validate_scan_mask()
already caps the number of active channels at num_slots.

This issue was found by an in-house static analysis tool.

The Linux kernel CVE team has assigned CVE-2026-98677 to this issue.


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

	Issue introduced in 5.19 with commit 8bea9af887de4c99a95f93f2ce400ef63e8b4e9b and fixed in 6.12.113 with commit 84500ae0d976995a6870cb1dca2d124b6b2d6e5a
	Issue introduced in 5.19 with commit 8bea9af887de4c99a95f93f2ce400ef63e8b4e9b and fixed in 6.18.56 with commit f20b94a7dc1ff9ade191ce839c984210fdbdc653
	Issue introduced in 5.19 with commit 8bea9af887de4c99a95f93f2ce400ef63e8b4e9b and fixed in 7.2.10 with commit 5663c72bf400231e90777982216797191887a6b9
	Issue introduced in 5.19 with commit 8bea9af887de4c99a95f93f2ce400ef63e8b4e9b and fixed in 7.3-rc6 with commit 9ee8306121495d2a25aa5d1bfd519f2748786b83

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-2026-98677
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/84500ae0d976995a6870cb1dca2d124b6b2d6e5a
	https://git.kernel.org/stable/c/f20b94a7dc1ff9ade191ce839c984210fdbdc653
	https://git.kernel.org/stable/c/5663c72bf400231e90777982216797191887a6b9
	https://git.kernel.org/stable/c/9ee8306121495d2a25aa5d1bfd519f2748786b83