From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-89985: memcg: keep folio's objcg same as its node
Date: Wed, 16 Sep 2026 11:31:55 +0100 [thread overview]
Message-ID: <2026091656-CVE-2026-89985-ef64@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
memcg: keep folio's objcg same as its node
memcg_reparent_objcgs() has an inherent assumption that a folio's objcg is
the objcg of the folio's node. Folio migration across nodes breaks that
assumption: the new folio simply inherits the old folio's objcg while
living on a different node.
Once the assumption is broken, the reparenting of the folio's objcg and
the reparenting of the folio's LRU list are no longer atomic.
memcg_reparent_objcgs() handles one node per iteration and drops all the
locks in between, so the objcg gets reparented in the iteration for the
objcg's node while the LRU list gets spliced in the iteration for the
folio's node. Any LRU operation on that folio in between resolves its
lruvec through the objcg, and thus takes the lru_lock of the wrong memcg,
not the lru_lock of the list the folio is actually on.
Fix this by selecting the objcg by folio_nid() at charge time, and by
re-deriving it for the destination node in mem_cgroup_migrate() and
mem_cgroup_replace_folio().
The Linux kernel CVE team has assigned CVE-2026-89985 to this issue.
Affected and fixed versions
===========================
Issue introduced in 7.1 with commit f1cf8d2f36dc369688bbe61ce064fbd829dbc9e1 and fixed in 7.2.5 with commit 6165478eaa3094eaee1d5e33b12520064faf043d
Issue introduced in 7.1 with commit f1cf8d2f36dc369688bbe61ce064fbd829dbc9e1 and fixed in 7.3-rc1 with commit bf4ade7dbd76d4ec8697840e4ebb15ed77c5ec26
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-2026-89985
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/memcontrol.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/6165478eaa3094eaee1d5e33b12520064faf043d
https://git.kernel.org/stable/c/bf4ade7dbd76d4ec8697840e4ebb15ed77c5ec26
reply other threads:[~2026-09-16 10:42 UTC|newest]
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