CVE-2026-93256: arm64: hibernate: mask DAIF before restoring hibernated kernel

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

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

arm64: hibernate: mask DAIF before restoring hibernated kernel

The arm64 hibernate code manages the exception masking in an unsound
way, leading to potential crashes and/or warnings during resume.

When a hibernation image is saved in `swsusp_arch_suspend()`, all DAIF
exceptions are masked (by virtue of `local_daif_save()`), and the
suspended image is saved assuming that all DAIF exceptions will remain
masked when the image is restored.

When a hibernation image is resumed by `swsusp_arch_resume()`, only
interrupts are masked (by virtue of `local_irq_disable()` in
`resume_target_kernel()`). When pseudo-NMI is enabled the DAIF.IF bits
will be clear, and regardless of pseudo-NMI the DAIF.DA bits will be
clear.

This means that there are two problems:

(1) It is possible to take Debug, SError, or pseudo-NMI exceptions
    during the resume process. This is unsafe, as during the resume
    process both the old ane new kernels will tranisently be in an
    inconsistent state, and swsusp_arch_suspend_exit() won't retain
    an executable mapping of any exception vectors.

    Any exception taken here will be fatal and silent.

(2) When re-entering the resumed kernel, some DAIF bits will be clear
    unexpectedly. This permits Debug, SError, or pseudo-NMI exceptions
    to be taken for a short period while the resumed kernel is not yet
    in a consistent state.

    This is detected by CONFIG_ARM64_DEBUG_PRIORITY_MASKING.

Avoid these issues by masking all DAIF exceptions during resume.

The Linux kernel CVE team has assigned CVE-2026-93256 to this issue.


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

	Issue introduced in 4.7 with commit 82869ac57b5d3b550446932c918dbf2caf020c9e and fixed in 5.10.270 with commit c9c671e9ab87b639720db8f7f8648bdf0f3bc8ec
	Issue introduced in 4.7 with commit 82869ac57b5d3b550446932c918dbf2caf020c9e and fixed in 5.15.221 with commit 099ad3edcef1d955d9f5d6aab16ae78ecdfd4cda
	Issue introduced in 4.7 with commit 82869ac57b5d3b550446932c918dbf2caf020c9e and fixed in 6.1.188 with commit 716c41bd476334afb943308be9ff2142e34461b7
	Issue introduced in 4.7 with commit 82869ac57b5d3b550446932c918dbf2caf020c9e and fixed in 6.6.157 with commit 5370853041a3cb53a125b77528586278f64b378b
	Issue introduced in 4.7 with commit 82869ac57b5d3b550446932c918dbf2caf020c9e and fixed in 6.12.110 with commit 290c5b0c9fc0c61fb1c41421ed2394f955206ea0
	Issue introduced in 4.7 with commit 82869ac57b5d3b550446932c918dbf2caf020c9e and fixed in 6.18.52 with commit 012823494e20c3cce622982ebd3fd6971be39ad2
	Issue introduced in 4.7 with commit 82869ac57b5d3b550446932c918dbf2caf020c9e and fixed in 7.2.6 with commit d736ace2c491623c9ab5e73744085e93e9ae3ebe
	Issue introduced in 4.7 with commit 82869ac57b5d3b550446932c918dbf2caf020c9e and fixed in 7.3-rc1 with commit 684bde100117931f4c51c644a95f42f2dab041bc

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-2026-93256
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:
	arch/arm64/kernel/hibernate.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/c9c671e9ab87b639720db8f7f8648bdf0f3bc8ec
	https://git.kernel.org/stable/c/099ad3edcef1d955d9f5d6aab16ae78ecdfd4cda
	https://git.kernel.org/stable/c/716c41bd476334afb943308be9ff2142e34461b7
	https://git.kernel.org/stable/c/5370853041a3cb53a125b77528586278f64b378b
	https://git.kernel.org/stable/c/290c5b0c9fc0c61fb1c41421ed2394f955206ea0
	https://git.kernel.org/stable/c/012823494e20c3cce622982ebd3fd6971be39ad2
	https://git.kernel.org/stable/c/d736ace2c491623c9ab5e73744085e93e9ae3ebe
	https://git.kernel.org/stable/c/684bde100117931f4c51c644a95f42f2dab041bc