CVE-2024-26618: arm64/sme: Always exit sme_alloc() early with existing storage

CVE-2024-26618: arm64/sme: Always exit sme_alloc() early with existing storage

[Lee Jones]

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

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

arm64/sme: Always exit sme_alloc() early with existing storage

When sme_alloc() is called with existing storage and we are not flushing we
will always allocate new storage, both leaking the existing storage and
corrupting the state. Fix this by separating the checks for flushing and
for existing storage as we do for SVE.

Callers that reallocate (eg, due to changing the vector length) should
call sme_free() themselves.

The Linux kernel CVE team has assigned CVE-2024-26618 to this issue.


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

	Issue introduced in 6.5 with commit 5d0a8d2fba50 and fixed in 6.6.15 with commit 569156e4fa34
	Issue introduced in 6.5 with commit 5d0a8d2fba50 and fixed in 6.7.3 with commit 814af6b4e600
	Issue introduced in 6.5 with commit 5d0a8d2fba50 and fixed in 6.8-rc1 with commit dc7eb8755797

Please see https://www.kernel.org or 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-2024-26618
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/fpsimd.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/569156e4fa347237f8fa2a7e935d860109c55ac4
	https://git.kernel.org/stable/c/814af6b4e6000e574e74d92197190edf07cc3680
	https://git.kernel.org/stable/c/dc7eb8755797ed41a0d1b5c0c39df3c8f401b3d9