In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
mm\/shrinker: fix bogus set_shrinker_bit() with cgroup.memory=nokmem<\/p>\n
With cgroup.memory=nokmem, shrinker_memcg_alloc() bails out early and
\nnever allocates an id, so shrinker->id keeps the 0 it got from the
\nkzalloc() in shrinker_alloc(). __list_lru_init() then copies that 0 into
\nlru->shrinker_id, where it looks like a valid bit index.<\/p>\n
Nothing calls expand_shrinker_info() on nokmem either, so shrinker_nr_max
\nstays 0 and every memcg ends up with an empty map (map_nr_max == 0).<\/p>\n
deferred_split_folio() hands a real memcg to __list_lru_add() regardless
\nof whether the lru is memcg aware, so the first THP queued in a cgroup
\ndoes set_shrinker_bit(memcg, nid, 0) and trips the bounds check:<\/p>\n
WARNING: mm\/shrinker.c:212 at set_shrinker_bit+0x7d\/0x90, CPU#126
\nCall Trace:<\/p>\n
deferred_split_folio+0x18c\/0x220
\n map_anon_folio_pmd_nopf+0xdd\/0x130
\n map_anon_folio_pmd_pf+0x14\/0xb0
\n do_huge_pmd_anonymous_page+0x1a1\/0x620
\n __handle_mm_fault+0xea9\/0x10d0
\n handle_mm_fault+0xe5\/0x320
\n do_user_addr_fault+0x1cc\/0x870
\n exc_page_fault+0x81\/0x1b0
\n asm_exc_page_fault+0x27\/0x30<\/p>\n
Harmless, the WARN_ON_ONCE() is what keeps the out of bounds unit[] read
\nfrom happening, but the id should not look valid in the first place.
\nClear it before returning.<\/p>\n
Two other spots could paper over this: drop the id in __list_lru_init()
\nwhen nokmem turns memcg_aware off, or make deferred_split_folio() pass
\nNULL like list_lru_add_obj() does. Both leave shrinker->id lying around
\nfor the next caller, so fix it where the id is handed out.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
mm\/shrinker: fix bogus set_shrinker_bit() with cgroup.memory=nokmem<\/p>\n
With cgroup.memory=nokmem, shrinker_memcg_alloc() bails out ea<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-33294","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/33294","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=33294"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=33294"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=33294"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}