CVE-2026-64592: riscv: mm: Unconditionally sfence.vma for spurious fault

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

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

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

riscv: mm: Unconditionally sfence.vma for spurious fault

Svvptc does not guarantee that it's safe to just return here. Since we
have already cleared our bit, if, theoretically, the bounded timeframe
for the accessed page to become valid still hasn't happened after sret,
we could fault again and actually crash.

Hopefully, these spurious faults should be rare enough that this is an
acceptable slowdown.

The Linux kernel CVE team has assigned CVE-2026-64592 to this issue.


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

	Issue introduced in 6.12 with commit 503638e0babf364061bc50fca5103b00a56cc50a and fixed in 6.12.96 with commit c4df24702bfc3cd2bed7746b94dc6139a3fa5428
	Issue introduced in 6.12 with commit 503638e0babf364061bc50fca5103b00a56cc50a and fixed in 6.18.39 with commit 4d730cab96e6b75e4a07c4baf37294ebc07f795e
	Issue introduced in 6.12 with commit 503638e0babf364061bc50fca5103b00a56cc50a and fixed in 7.1.4 with commit ede985ff4b569ed2454024f8bb107a6729fe08aa
	Issue introduced in 6.12 with commit 503638e0babf364061bc50fca5103b00a56cc50a and fixed in 7.2-rc1 with commit 1b2c6b56a9fa0dcbef461039937de22b1cbecc7d

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-2026-64592
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/riscv/kernel/entry.S


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/c4df24702bfc3cd2bed7746b94dc6139a3fa5428
	https://git.kernel.org/stable/c/4d730cab96e6b75e4a07c4baf37294ebc07f795e
	https://git.kernel.org/stable/c/ede985ff4b569ed2454024f8bb107a6729fe08aa
	https://git.kernel.org/stable/c/1b2c6b56a9fa0dcbef461039937de22b1cbecc7d