linux-cve-announce - CVE-2025-71110: mm/slub: reset KASAN tag in defer

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Message-ID: <2026011412-CVE-2025-71110-c354@gregkh>
Date: Wed, 14 Jan 2026 16:06:15 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-71110: mm/slub: reset KASAN tag in defer_free() before accessing freed memory

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

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

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

mm/slub: reset KASAN tag in defer_free() before accessing freed memory

When CONFIG_SLUB_TINY is enabled, kfree_nolock() calls kasan_slab_free()
before defer_free(). On ARM64 with MTE (Memory Tagging Extension),
kasan_slab_free() poisons the memory and changes the tag from the
original (e.g., 0xf3) to a poison tag (0xfe).

When defer_free() then tries to write to the freed object to build the
deferred free list via llist_add(), the pointer still has the old tag,
causing a tag mismatch and triggering a KASAN use-after-free report:

  BUG: KASAN: slab-use-after-free in defer_free+0x3c/0xbc mm/slub.c:6537
  Write at addr f3f000000854f020 by task kworker/u8:6/983
  Pointer tag: [f3], memory tag: [fe]

Fix this by calling kasan_reset_tag() before accessing the freed memory.
This is safe because defer_free() is part of the allocator itself and is
expected to manipulate freed memory for bookkeeping purposes.

The Linux kernel CVE team has assigned CVE-2025-71110 to this issue.


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

	Issue introduced in 6.18 with commit af92793e52c3a99b828ed4bdd277fd3e11c18d08 and fixed in 6.18.3 with commit 65d4e5af2a2e82f4fc50d8259aee208fbc6b2c1d
	Issue introduced in 6.18 with commit af92793e52c3a99b828ed4bdd277fd3e11c18d08 and fixed in 6.19-rc2 with commit 53ca00a19d345197a37a1bf552e8d1e7b091666c

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-2025-71110
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:
	mm/slub.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/65d4e5af2a2e82f4fc50d8259aee208fbc6b2c1d
	https://git.kernel.org/stable/c/53ca00a19d345197a37a1bf552e8d1e7b091666c