CVE-2026-98225

What the bug is

With cgroup.memory=nokmem, shrinker_memcg_alloc() bails out early and never allocates an id, so shrinker->id keeps the 0 it got from the kzalloc() in shrinker_alloc(). __list_lru_init() then copies that 0 into lru->shrinker_id, where it looks like a valid bit index. Nothing calls expand_shrinker_info() on nokmem either, so shrinker_nr_max stays 0 and every memcg ends up with an empty map (map_nr_max == 0). deferred_split_folio() hands a real memcg to __list_lru_add() regardless of whether the lru is memcg aware, so the first THP queued in a cgroup does set_shrinker_bit(memcg, nid, 0) and trips the bounds check: WARNING: mm/shrinker.c:212 at set_shrinker_bit+0x7d/0x90, CPU#126 Call Trace: <TASK> deferred_split_folio+0x18c/0x220 map_anon_folio_pmd_nopf+0xdd/0x130 map_anon_folio_pmd_pf+0x14/0xb0 do_huge_pmd_anonymous_page+0x1a1/0x620 __handle_mm_fault+0xea9/0x10d0 handle_mm_fault+0xe5/0x320 do_user_addr_fault+0x1cc/0x870 exc_page_fault+0x81/0x1b0 asm_exc_page_fault+0x27/0x30 </TASK> Harmless, the WARN_ON_ONCE() is what keeps the out of bounds unit[] read from happening, but the id should not look valid in the first place. Clear it before returning. Two other spots could paper over this: drop the id in __list_lru_init() when nokmem turns memcg_aware off, or make deferred_split_folio() pass NULL like list_lru_add_obj() does. Both leave shrinker->id lying around for the next caller, so fix it where the id is handed out.

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

mm/shrinker.c

What this is

SHRINKERMAINTAINERS section matched on mm/shrinker.c · linux-mm@kvack.org · Maintained

Show whether Debian builds this, per release

Debian builds this code. Every release with an answer below compiles the affected file into the kernels it ships. The build rule could not be established for 1 release, so nothing is claimed about those.

• bookworm?
• trixie, forky, sidy

?

not established - no Makefile entry for the affected file

y

built into the kernel image on every flavour - only a patch removes it

Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS Debian linux-config packages

Signals

Published

2026-10-06 (13 days ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.16%, higher than 5.0% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

unimportantsource

Subsystem

mm

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
7.2	7.2.8	469c12a69ab1
7.2	7.3	932cfb25e7ce